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USER'S GUIDE TO SURFMODL 3.00C By Kenneth E. Van Camp November, 1991 TABLE OF CONTENTS INTRODUCTION ............................................... 2 REFERENCES ................................................. 3 USING SURFMODL ............................................. 4 INTERACTIVE OPERATION ...................................... 5 CONFIGURATION/INITIALIZATION FILE FORMAT ................... 9 SURFMODL DATA FILE FORMAT ..................................11 USING PREPROC ..............................................13 PREPROC DATA FILE FORMAT ...................................15 USING PLAYBACK .............................................19 USING REVOLUTION ...........................................21 USING SURFEDIT .............................................23 PRINTING THE SCREEN ........................................25 INSTRUCTIONS FOR RECOMPILING SURFMODL 2.00C ................26 INTERPRETATION OF ERROR MESSAGES ...........................27 SURFMODL USER REGISTRATION .................................29 UPGRADING SURFMODL .........................................30 INTRODUCTION Surface modeling is the science of producing realistic three- dimensional images on a computer display. SURFMODL is a public domain surface modeling program that runs on the IBM PC and most compatibles. Specifically, it supports the IBM CGA, MCGA, EGA, VGA, PC3270, AT&T 6300, and Hercules graphics adapters. There is also limited support for the DEC VAXMATE and Commodore Amiga computers. Earlier versions of SURFMODL (versions 1.32 and earlier) also supported the Sanyo MBC-550 and Heath/Zenith Z100; this support does not presently exist in version 3.00C. SURFMODL requires only 256K RAM, runs amazingly fast, and is a general- purpose surface modeler. It creates displays of three-dimensional wire frame images, removes hidden lines, and performs surface modeling. Since it is a generalized program, it can be used to view any object from any angle, with single or multiple light sources. It is accompanied by PREPROC (a general-purpose non- interactive preprocessor), REVOLUTE (a special-purpose interactive preprocessor for generating objects of revolution), SURFEDIT (a general-purpose interactive data file editor), 3DSURF (a special- purpose preprocessor for generating 3-D function data files), PLAYBACK (a general-purpose program to replay saved SURFMODL screens to create animations and demonstrations), and PLAYPAL (a program to allow experimentation with the color palette of a VGA or Super VGA). This file contains instructions for the use of most of these. Source code for all of these utilities (over 5000 lines of Turbo Pascal source code) are included on the distribution diskettes. At the end of this file are some special notes on becoming a registered user of SURFMODL (for free). SURFMODL is placed in the public domain. SURFMODL may be freely distributed, or distributed at nominal copying/mailing fee, but may not be otherwise charged for. No warranty is provided, either express or implied. SURFMODL may not be incorporated into commercial software without express written permission of the principle author: Kenneth Van Camp RD #1 Box 1255 East Stroudsburg, PA 18301 U.S.A. Surface modeling is often confused with solids modeling, which encompasses surface modeling but includes much more. The pictorial results are often equivalent, however, so the distinction is not important if the objective is to produce spectacular graphics. To use common solid modeling terminology, SURFMODL is a boundary representation (B-Rep) solid modeler for flat surfaces of any number of sides. (All surfaces are polygons of any order.) Applications of surface modeling are many and growing. SURFMODL was originally written to display finite element data and plots of three-dimensional curves. Computer-aided styling, general CAD/CAM, and artistic rendering are among the many applications at which SURFMODL excells. If you would like to learn more about SURFMODL, beyond this user's guide, there are several references provided below. REFERENCES 1. Bickel, Marilyn and Sheppard, Gene, "A Simple 3-D Surface", Journal of Pascal, ADA & Modula-2, Nov/Dec 1985, 12-23. 2. Haroney, George, "Graphing Quadric Surfaces", Byte, Dec. 1986, 215-224. 3. Crow, Franklin gw, "Shadow Algorithms for Computer Graphics", Computer Graphics, Vol. 11 No. 2, Summer 1977. 4. Newman, William M. and Sproull, Robert F., Principles of Interactive Computer Graphics, 2d ed., McGraw-Hill, New York, 1979. USING SURFMODL When used in conjunction with a finite element preprocessor, a special-purpose function generation routine, or one of SURFMODL's preprocessors, SURFMODL is a complete surface modeling system, capable of constructing models of any variety of objects of virtually unlimited complexity. Because SURFMODL is in the public domain, and is distributed with full source code, it has attracted the attention of many PC hackers, as well as educators. (There are at least two teachers now using SURFMODL in their computer graphics classes.) SURFMODL has the distinction of running on many different MSDOS systems, due to the support it has received from many users worldwide. Special recognition should be given to Kevin Lowey, who converted SURFMODL and PREPROC to run under Turbo Pascal 4.0. Kevin also wrote PLAYBACK, added SURFMODL support for the Borland Graphics Interface (BGI) device independent graphics, and made several other enhancements to the program. Ian Murphy should also be recognized, for his work adding support for heap memory (to drastically increase the maximum number of surfaces SURFMODL can handle on machines with at least 512K RAM), and for writing REVOLUTE and SURFEDIT. Both of these programs, incidentally, must still be compiled under Turbo Pascal 3.01A; the rest of the programs in this package must be compiled under Turbo Pascal 4.0 or higher. See the file 300NOTES.TXT for notes about compiling this release. Amnon Levav should also be recognized, for writing the 3DSURF program. With version 3.0, the limit on the complexity of the object SURFMODL can model is no longer dependent on how it was compiled. SURFMODL dynamically allocates all the major arrays in the program, so you can run as large a model as will fit in your computer's conventional memory. (There is no support for extended or expanded memory in SURFMODL, but PLAYBACK supports extended memory for longer animations.) INTERACTIVE OPERATION Invoking SURFMODL from DOS is accomplished by a command of the form: SURFMODL [filename [menuopt [keystroke]]] where the filename is the optional specification of a SURFMODL data file. If a filename is not specified on the command line, it must be read by menu options. If a filename is specified on the command line, it is read in immediately. If a menu option is also specified on the command line, then SURFMODL bypasses the title screen and main menu and immediately draws the screen. This can be useful for demonstrations, or automating SURFMODL usage through batch files. Legal values for menuopt are 2, 3 or 4. Finally, if a menu option is given on the command line, then you can also optionally add a single-letter keystroke that tells SURFMODL what to do when it is all done plotting. Currently the only keystroke that makes any sense to use here is 'f', which means that SURFMODL should automatically save the screen to a file and exit when it is done plotting. (See MOLECULE.DOC and MKMOVIE.BAT for an example of how to use this.) When SURFMODL is started without the menuopt parameter, or with no parameters at all, the main menu appears. Menu options are selected by pressing the number corresponding to the option desired. Option 0 always returns to the previous menu or, in the case of the main menu, exits the program. Pressing the space bar or escape key is equivalent to pressing 0. Option 5 of the main menu is generally the one you will start with. It brings up a file selector box to allow you to choose a data file. It searches the current directory for all files with a '.SRF' extension. (However, if you set a value for the environment variable SURFDIR prior to starting SURFMODL, the program will search in that directory instead of the current directory.) Options 2, 3 and 4 of the main menu will start the plotting of the selected data set in wire frame, hidden line removal, or surface modeling. During plotting, any time the user hits the 'A' key, the plot is aborted and the main menu is returned. When plotting is complete, the program will wait for a keypress before returning to the main menu. In general, any keypress will return the main menu; however there are two special keys: F and P. The 'F' key causes the current screen to be saved in a binary file called 'myfile.1', where we are assuming the original data file was called 'myfile.SRF'. Actually, what happens here is that SURFMODL checks for the existence of the file 'myfile.1' before creating it; if that file already exists then it tries 'myfile.2', etc. This allows you to do several screen saves without having to worry about overwriting your old data files. PICture files can be replayed with a special program called PLAYBACK (described later in this documentation). PICTURE FILES ARE SPECIFIC TO THE GRAPHICS DEVICE BEING USED, and cannot be used on other devices. The 'P' key enters a pause mode, whereby all keystrokes are ignored except the letter 'P', which then exits the pause mode. Then any other keystroke brings up the main menu. Option 1 of the main menu selects the parameters menu. This menu allows the user to change numerous viewing, system, and file parameters, and to save any of these parameters to disk. All numeric inputs in the menus have a common prompt. You are presented with the name of the input, the value presently being used, and an equal sign. For instance, the prompt to enter a new X coordinate for the eye looks like: X of Eye ( 100.0 ) = Hitting just the <return> key will keep the old value (in this case, 100). Typing any number instead will make that be the new value used. There are six options in the parameters menu. Options 2 and 3 set up the viewing angles by selecting three-dimensional coordinates of the viewer's eye and focal point. The distance between the eye and focal point is important, since SURFMODL uses perspective plotting. To start, always place the eye far from the focal point to avoid excessive distortion. The focal point is important because this point is always placed at the center of the screen. If the focal point is placed so that it lies outside the limits of the object, a warning message will be issued. This does not necessarily mean the plot will not be visible, but is merely meant to warn the user that his plot may not be within the limits of the screen. If a blank screen results, the user should move the focal point closer to the center of the object. Option 4 selects the magnification factor. A magnification of 1 makes the plot as large as possible without exceeding the screen limits in either the X or Y direction. To zoom in on a particular area of the figure, be sure to move the focal point to that area to center it on the screen, then gradually increase the magnification. Option 5 of the parameters menu selects the view type. By default, all plots are made in perspective view (selection 0). This is almost always the option you should choose. The only time a non-perspective drawing is done is when one of the orthogonal views is selected (X-Y, X-Z, or Y-Z). In this case, the eye coordinates are ignored. After selecting a view type, you will be asked if you want to show the axes. Typing Y will place coordinate system axes, labeled X, Y and Z at the lower left corner of all plots subsequently produced. This can be useful when trying to decide how to adjust eye coordinates. If you select axis drawing, you will be asked for the length to draw the axes in the X, Y and Z directions. These numbers are input in world coordinates, and should generally be about 10-20% of the maximum dimension in the data file. Finally, you are asked for a color to draw the axes. Again, make sure you choose a valid color for your system. Option 6 saves all of your current settings to a file with the same name as your data file, but with an extension of .INI. When a new data file is read with option 5 of the main menu (or specified on the command line), SURFMODL automatically searches the disk for the .INI file. If it exists, it is read in and used to initialize numerous parameters. Every setting in the parameters menu and the lighting menu is copied into the .INI file, plus there are some others that are not available in the menus but can be manually typed in by editing the .INI file. See the section on Configuration/Initialization files. There is a small redundancy between the main data file and the .INI file. Material properties can be set either in the main data file or in the lighting menu, and are therefore saved in the .INI file. Since the .INI file is read after the main file, the material properties saved in the .INI file will be the final ones used in the program. Option 1 of the parameters menu selects the lighting menu. The lighting menu has five options. Option 1 of the lighting menu allows the user to change material properties. The user should know what material numbers were specified for the surfaces in the data file. R1, R2 and R3 are reflectivity constants, which are used in the equation for the reflected light intensity: E = I[R1(cos s)**R2 + R3cos n] + Ambient where I is the incident light intensity, s is the angle between the reflected light vector and the line of sight, n is the angle between the light source and the surface normal (i.e., independent of the viewing angle), and **R2 means "raised to the R2 power". The ambient light intensity can be set for each material individually, so that different parts of the solid can be given different intensities. (This is one way to make a piece of an object stand out against the background of another piece. It can also be used to give the illusion of different colors on a monochrome monitor.) Light intensity is a real number between zero and one, with zero corresponding to black and one to white. Ambient light is usually set to a low level of around 0.1 - 0.3. The color selected for the material is used for wireframe and hidden line plots, and for surface modeling if the dithering option is selected. Entering a color number of 0 brings up three additional prompts, for the Red, Green and Blue values. These values are only used on VGA systems, or for the special Amiga IFF version of SURFMODL, SURFIFF (see SURFIFF.DOC for details). These values should be in the range from 1 to 256, with representing no color and 256 representing full color intensity. To help you experiment to find the best color combinations for your SURFMODL files, there is a special utility called PLAYPAL. There is no documentation on this utility, but it should be fairly self- explanatory (there is a help screen by pressing F1). Option 2 changes the light source data. Light source number one is the primary light source, and is the one used for shadowing calculations. The first prompt at this option is for the light source number. Entering a zero will delete the last light source (if there is more than one). You may add a new light source by entering a number that is one greater than the current number of light sources. The user is prompted for the new coordinates of the light source, and the intensity associated with it. As before, this number is usually between zero and one, although larger numbers can be used for very bright lighting. On color monitors (other than the VGA in 256-color mode), the dithering tends to darken the picture, so you may want to experiment with brighter lighting. If the lighting is too bright, the picture will become washed out and features will be indistinguishable. Option 3 changes Epsilon, the constant for Gouraud interpolation (smoothing). Entering zero will result in no interpolation whatsoever. Entering any other value will invoke the Gouraud interpolation option. This is a simple 3-dimensional interpolation scheme that will artificially "smooth out" shading of curved objects. Because SURFMODL uses flat surfaces for all plotting, curved objects (like FACES.SRF, the data file on the distribution diskette of my wife's face) normally look very patchy. The Gouraud option will smooth this out by averaging shading at the nodes and interpolating between them. The only problem with Gouraud interpolation is that sharp corners (which you may desire) tend to get washed out and look rounded. Therefore, Epsilon is a difference option. If the shades of any neighboring surfaces differ by more than Epsilon, they are not interpolated. A good value of Epsilon is usually around 0.3, but other values may be necessary for special cases. If you selected the Gouraud option (by entering a value of Epsilon greater than 0), then you are next prompted for a random shading value. The user is encouraged to enter a random shade of 0 the first time he views any Gouraud-interpolated image. If you find that the interpolation has created sharp lines of definition between neighboring shades, then you may want to go back and add a random shade (RandShade). The number you enter for RandShade causes SURFMODL to randomly select a number in the range of 0 - RandShade for each pixel, and add it to the lighting value for that pixel. RandShade should never be greater than one. Option 4 selects (or deselects) the shadowing option. This option will significantly increase computation time, so it should not be used until all viewing and lighting angles have been thoroughly tested. This option has never worked very well, so I usually disable it in the executable I send out in releases (this saves quite a bit of memory). CONFIGURATION/INITIALIZATION FILE FORMAT There are two types of files discussed in this section. One is the SURFMODL configuration file, and the other is the data initialization files. In fact, these two files have identical formats and have a good deal of overlap in functionality. Here's the specifics: When SURFMODL is started, it looks for a file called SURFMODL.CFG. If it doesn't find it in the current directory, then it checks to see if you have defined an environment variable called SURFDIR (see your MSDOS manual's explanation of the SET command), and if so uses the specified directory for locating SURFMODL.CFG. If it doesn't find SURFMODL.CFG, it kicks you out. If it does find SURFMODL.CFG, that file is read and all the options in the file are used to initialize many parameters. Most important of these is GRSYS and GRMODE, which set the graphic system type and graphics mode to plot in. SURFMODL.CFG is most easily created by running the installation program, SURFINST, but if you want you can create it manually. SURFINST will automatically detect your system type, and present you with a menu of available graphics modes for your system (if there is more than one). When you read in a new file (either by specifying it on the command line or through the file selector), SURFMODL checks for a file of the same name with a .INI extension. If it exists, all parameters saved in the file are read and used to set up the next plot. The .INI file is normally created by using the "Save Parameters" option in the Parameters Menu. Since SURFMODL.CFG and the .INI files share many of the same commands, you can use SURFMODL.CFG to set defaults for how you usually like to view files. And since the .INI files are always read AFTER the SURFMODL.CFG file, any parameters you save in there will override the SURFMODL.CFG file whenever you read in that data file. OK, enough about usage. The file format is pretty simple, and includes a number of symbolic commands. Like all the SURFMODL data files, an asterisk in the first column of any line makes that line a comment, and it is ignored. Otherwise, all lines must be of the format: cmmd: parameters where 'cmmd' is one of the valid commands, listed below. All commands are in capital letters, and you MUST type them that way; SURFMODL will not recognize these commands in lower case. Of course, you normally will not type in these lines at all, since the file will be created automatically with the "Save Parameters" option. You might want to edit it to change some values, however, since there are some options available through the .INI files that are not available through the menus. (The converse is not true, however; all menu parameters are saved in the .INI file.) Here is a summary of the available commands. An asterisk next to the command name means it is valid in both the SURFMODL.CFG file and the .INI files; two asterisks means it is only valid in the SURFMODL.CFG file; no asterisks means it is only valid in the .INI files. Some of the parameters are symbolic, while others are numeric. Where they are symbolic, I have followed the description with a list of valid symbols, enclosed in braces ({}). For example, { ON, OFF } means that valid parameters are the words "ON" or "OFF" (case-sensitive, again). COMMAND PARAMETERS DESCRIPTION **GRSYS system Graphic System Type **GRMODE mode Graphics Mode *VERSION num Version Number of .CFG/.INI file *EYE x y z Coordinates of eye *FOCAL x y z Coordinates of focal point *MAGNIFY val Magnification factor *VIEWTYPE type View Type { STD, XY, YZ, XZ } MATL n Set Material Number (applies to all following MAT* commands) MATCONST r1 r2 r3 Set Material Constants MATCOLOR n Color to plot material MATAMBIENT val Ambient light intensity MATRGB r g b Set RGB values for color (overrides MATCOLOR on VGA systems) *LIGHT n Set Light Number (applies to all following LT* commands) *LTCOORD x y z Set Light Source Position *LTINTENS val Light Source Intensity *GOURAUD epsilon Epsilon, or 0 if no smoothing *SHADOWING opt Select Shadowing Option? { ON, OFF } *AXISSHOW opt Show Axes? { ON, OFF } *AXISLEN x y z Length of 3 axes to draw *AXISCOLOR n Color to plot axes *RANDOM randshade Random number to add to all shades (0 to turn off option) *BORDERS opt Show the borders of all surfaces? { ON, OFF } *TEXTCOL n Color# to use in text mode *BGCOL n Background color# in text mode *GRAPHTEXT n Color# to display title on plots **REVVIDEO opt Reverse all text video? { ON, OFF } *SHOWTITLE opt Show title on plot? { ON, OFF } **XYADJUST val X-Y Adjustment factor (changes aspect ratio of screen) SURFMODL DATA FILE FORMAT All input in the main data file is line oriented, in free format. The separator between lines is a carriage return, and the separator between data items on a line is a space, tab or comma. Any line that begins with an asterisk (*) in the first column is a comment, and is ignored. This is true anywhere AFTER the first line of the file, which contains the Title for the file. If you put an asterisk on the first line, you'll just get a title that starts with an asterisk. The data file can be created in any ASCII line editor (like Edlin, or the Turbo Pascal editor), or by one of the SURFMODL preprocessors. Following is the format for the main data file. Numbers in brackets indicate the range of legal inputs. Title Line (The first line of the data file is the title of the plot.) Version Line Variable Description Type VERSION Version Number of SURFMODL data file format [4] Integer (This set of instructions is for data file format number 4.) Control Line Variable Description Type NMATL Total number of materials in solid [1..20] Integer NNODES Total number of nodes in solid [1..1024] Integer NSURF Total number of surfaces in solid [1..3000/MAXV] Integer MAXVERT Maximum number of vertices in any one surface Integer NSIDES Number of sides of the surface to use [1..2] Integer A note on NSIDES: For most objects, use NSIDES=1 to get the fastest plotting. NSIDES=2 is really only provided for plotting three dimensional functions, and other objects that really don't have any "depth" (i.e., the surfaces have a thickness of 0). For normal objects (NSIDES=1), the "visible side" of a surface is defined as the one that is visible when viewing the surface from a side such that the nodes are numbered in a counter-clockwise direction. When SURFMODL computes the angle of a surface relative to the eye (which it does for both hidden line and shaded plots), it will not plot any surfaces that are at an angle of greater than 90 degrees from the eye vector (to save plotting time). If you set NSIDES=2, then SURFMODL will use BOTH sides of the surface, so every surface is guaranteed to be plotted, whether it faces the eye or not. (The counter-clockwise rule then doesn't matter.) Material Data (NMATL lines) Variable Description Type R1 First constant of material reflectivity [0..1] Real R2 Second constant of material reflectivity Real R3 Third constant of material reflectivity [0..1] Real COLOR Color # to use for wireframe plotting [1..3] Integer AMBIENT Ambient light intensity [0..1] Real Nodal Coordinate Data (NNODES lines) Variable Description Type XWORLD World X coordinate of node Real YWORLD World Y coordinate of node Real ZWORLD World Z coordinate of node Real Surface Connectivity Data (NSURF lines) (NOTE: Connectivity data may be continued onto multiple lines.) Variable Description Type NVERT Number of vertices in this surface [3..MAXVERT) Integer MATL Material number of this surface [1..NMATL] Integer NODE1 Node number of the first vertex [1..NNODES] Integer NODE2 Node number of the second vertex [1..NNODES] Integer . . . . . . . . . NODE nvert Node number of the Nverth vertex [1..NNODES] Integer USING PREPROC PREPROC is a special-purpose preprocessor for SURFMODL. It allows the user to quickly generate SURFMODL data files consisting of objects of revolution, extrusion and simple planes. It also allows multiple SURFMODL data files to be easily combined. PREPROC is not interactive; nor is it graphical. However, the user will find it makes certain classes of objects very easy to create. An example PREPROC input file, FAN.IN, is on the distribution diskette with SURFMODL. The resulting SURFMODL data file, FAN.SRF, can be easily created by running PREPROC. For a more elaborate PREPROC example, see the file MOLECULE.DOC for instructions on how to recreate the APPLE.SRF file that was provided with the release. Before describing the details of the preprocessor data file, it is important to make a few notes. A PREPROC data file consists of three major sections: (1) the initial information, consisting of the title of the plot, control variables, and material data; (2) codes for the input of one or more solids; and (3) an ending code (0) marking the end of the input file. If PREPROC is only being used to combine two or more old SURFMODL data files, then it is not necessary to specify material data in the initial section. Material constants will be used from the individual data files, and PREPROC will automatically give them unique numbers to avoid conflicts. Actually, there is one exception to this rule. If PREPROC is started with the /R command-line option then this forces material numbers to be "re-used" when SURFMODL data files are read in. This is used in the molecule example; in this case the material numbers are the same in each file and apply globally to all the data files. When generating planes or objects of revolution or extrusion, material constants must be specified in the initial section. Any plane or object of revolution or extrusion can be scaled, shifted or rotated in any of the three principle directions. It is important to note the order in which these operations occur (in case more than one is used in a single object). First, the object is rotated. Then it is shifted, and finally scaled. Orientation codes are also provided to allow the user to easily orient an object of revolution or extrusion about one of the major axes. This is actually redundant to the use of the rotation angles, but is provided to make complex objects a little easier to generate. An orientation code can be 1, 2 or 3, corresponding to the X, Y or Z axis, respectively. The designated axis will then be the major axis of the object (the axis of revolution or extrusion). It is important to note that we will refer to R-Z coordinates when speaking of objects of revolution, and X-Y-Z coordinates when speaking of objects of extrusion. These are not to be taken as true X-Y-Z coordinates unless an orientation code of 3 is used. If a different code is specified, then the major axis (referred to as 'Z' below), becomes whichever one is requested. The other two axes are rotated to maintain a right- handed system. Objects of revolution are specified by giving the R and Z coordinates of any number of outline points. Once an outline is defined, it is rotated about the major axis, generating as many intermediate "slices" as specified by NSLICE. Objects of extrusion are formed by specifying a top and bottom Z coordinate for the two endplanes. Then the coordinates of the endplanes are given, in any amount of detail. NOUTLN specifies the number of points to be used to describe the outline of the endplanes. NEXTRUDE tells how many "slices" to break the object into in the Z direction. IQUAD is an option which, when selected (1), tells PREPROC to break down the two endplanes into quadrilaterals (to save storage space so you may keep MAXVERT=4). When deselected (0), IQUAD tells PREPROC to keep your two endplanes exactly as you specified them. The Planes option is merely to allow placement of large quadrilateral surfaces, broken down into many smaller quads. This is useful to add a "floor" to an existing data set -- for instance if you want to experiment with shadowing. The user specifies four sets of coordinates for the corners of a quad, and the number of smaller quads to break it into. The numbers NX and NY have nothing to do with actual X and Y coordinates, but are merely to give a count of the number of smaller quads to use in the two directions along the larger quad. The four corners must be specified in order so they form a counter-clockwise circular path when viewed from the visible side of the surface. NX refers to the number of breaks in the direction traveled from node 1 to node 2; NY refers to the other direction. When using PREPROC to combine two or more old SURFMODL data files, material data sets will be added for each surface unless the /R option is used. This is to avoid any conflicts between different material data sets. Invoking PREPROC from DOS is accomplished by a command of the form: PREPROC [/R] infile outfile where infile is the name of the PREPROC data file, and outfile is the name to be assigned to the output data file. For instance, to preprocess the FAN.IN file, type: PREPROC FAN.IN FAN.SRF (Note that the extension .IN is arbitrary and can be replaced by anything desired. The .SRF extension on the output file is recommended, since that is what SURFMODL looks for when bringing up the file selector.) PREPROC DATA FILE FORMAT All input in the preprocessor data file is line oriented, in free format. Following is the format for the preprocessor data file. Numbers in brackets show the range of legal inputs. Title Line (The first line of the data file is the title of the plot.) Version Line Variable Description Type VERSION Version Number of PREPROC data file format [2] Integer (This set of instructions is for data file format number 2.) Control Line Variable Description Type NMATL Total number of materials in solid [0..20] Integer MAXVERT Maximum number of vertices in any one surface Integer NSIDES Number of sides of the surface to use [1..2] Integer Material Data (NMATL lines) Variable Description Type R1 First constant of material reflectivity [0..1] Real R2 Second constant of material reflectivity Real R3 Third constant of material reflectivity [0..1] Real COLOR Color # to use for wireframe plotting [1..3] Integer AMBIENT Ambient light intensity [0..1] Real [The remaining set of data lines may be repeated as needed until all data has been inputted.] Shape Code Variable Description Type CODE Shape Code: 0 - End of data Integer 1 - Read old SURFMODL data file 2 - Surface of revolution 3 - Surface of extrusion 4 - Planar quadrilateral surface READFILE Control Line (Include this section if CODE = 1.) (This line should contain the name of a SURFMODL data file to be read in.) Scale & Shift Line Variable Description Type XSCALE Scaling factor in X direction Real YSCALE Scaling factor in Y direction Real ZSCALE Scaling factor in Z direction Real XSHIFT Displacement in X direction Real YSHIFT Displacement in Y direction Real ZSHIFT Displacement in Z direction Real Rotate Line Variable Description Type XROTATE Rotation about X axis (degrees) [-360..360] Real YROTATE Rotation about Y axis (degrees) [-360..360] Real ZROTATE Rotation about Z axis (degrees) [-360..360] Real REVOLVE Control Line (Include this section if CODE = 2.) Variable Description Type NOUTLN Number of points describing outline of surface Integer NSLICE Number of angular slices to create [1..] Integer MATERIAL Material number of this surface [1..20] Integer ORIENT Orientation code [1..3] Integer Scale & Shift Line Variable Description Type XSCALE Scaling factor in X direction Real YSCALE Scaling factor in Y direction Real ZSCALE Scaling factor in Z direction Real XSHIFT Displacement in X direction Real YSHIFT Displacement in Y direction Real ZSHIFT Displacement in Z direction Real Rotate Line Variable Description Type XROTATE Rotation about X axis (degrees) [-360..360] Real YROTATE Rotation about Y axis (degrees) [-360..360] Real ZROTATE Rotation about Z axis (degrees) [-360..360] Real Outline Coordinates (NOUTLN lines) Variable Description Type R R coordinate Real Z Z coordinate Real EXTRUDE Control Line (Include this section if CODE = 3.) Variable Description Type NOUTLN Number of points describing outline of surface Integer NEXTRUDE Number of Z slices to create [1..] Integer IQUAD Quadrilaterals option [1..2] Integer MATERIAL Material number of this surface [1..20] Integer ORIENT Orientation code [1..3] Integer Scale & Shift Line Variable Description Type XSCALE Scaling factor in X direction Real YSCALE Scaling factor in Y direction Real ZSCALE Scaling factor in Z direction Real XSHIFT Displacement in X direction Real YSHIFT Displacement in Y direction Real ZSHIFT Displacement in Z direction Real Rotate Line Variable Description Type XROTATE Rotation about X axis (degrees) [-360..360] Real YROTATE Rotation about Y axis (degrees) [-360..360] Real ZROTATE Rotation about Z axis (degrees) [-360..360] Real Top & Bottom Z Coordinates Variable Description Type ZTOP Z coordinate of top surface Real ZBOT Z coordinate of bottom surface Real Outline Coordinates (NOUTLN lines) Variable Description Type X X coordinate Real Y Y coordinate Real PLANE Control Line (Include this section if CODE = 4.) Variable Description Type NX Number of quads to break down - X [1..] Integer NY Number of quads to break down - Y [1..] Integer MATERIAL Material number of this surface [1..20] Integer Scale & Shift Line Variable Description Type XSCALE Scaling factor in X direction Real YSCALE Scaling factor in Y direction Real ZSCALE Scaling factor in Z direction Real XSHIFT Displacement in X direction Real YSHIFT Displacement in Y direction Real ZSHIFT Displacement in Z direction Real Corner Coordinates (include 4 lines) Variable Description Type X X coordinate of corner Real Y Y coordinate of corner Real Z Z coordinate of corner Real USING PLAYBACK PLAYBACK is a screen reviewing utility for SURFMODL, written by Kevin Lowey. It allows you to create animated images by playing back SURFMODL PICture files, which were created by hitting the 'F' key in SURFMODL after a picture is generated on the screen. Then you can replay any screen, or any sequence of screens, using PLAYBACK. If you just type 'PLAYBACK' and hit Enter, the program will provide some brief instructions. What it will tell you is that you should have specified a control file on the command line, as in: PLAYBACK ctrlfile where 'ctrlfile' should be replaced by the name of a control file you create. In this control file, you will specify the names of SURFMODL PICture files that you have previously generated, along with a couple of options for displaying the files. There is an important limitation to the PLAYBACK command: files that were saved on a system with one type of graphics adapter can only be replayed on systems with the same type of graphics adapter. This is because the PICture files are specific to the hardware being used. You cannot, for instance, play back a PICture file on a Hercules graphics adapter that was created on an EGA system. The control file format is extremely simple. One line is used to specify each file name; the format is "DELAY DISPLAYMODE FILENAME" for each line. The three entries must be separated by at least one space. The delay is a time, in milliseconds (1/1000 of a second), to show the file before proceeding to the next one. Specifying a delay of -1 will cause PLAYBACK to wait for a keypress before proceeding; a delay of -2 causes PLAYBACK to go back to the beginning screen and replay all the images again. This causes an infinite loop, which is exited when any key is pressed. Similarly, a delay of -3 causes an infinite loop, but in which the the images are displayed in reverse order until they reach the first image. Then it displays them in forward order, etc., so that an oscillating animation can be created. The display mode is an integer code between 0 and 4, as follows: 0 : Normal mode, image replaces image on screen. 1 : XOR mode, Shows image EXCEPT where it matches screen. 2 : OR mode, Shows both image and screen. 3 : AND mode, Shows only where image and screen intersect. 4 : NOT mode, Shows the inverse of the image. For instance, suppose you had saved three PICture files consisting of images of the fan in different angles of rotation. And suppose you had named these files FAN.1, FAN.2, and FAN.3. You could replay all three of them, with one-second pauses between, by creating a playback control file as follows: 1000 0 FAN.1 1000 0 FAN.2 1000 0 FAN.3 To create a continuous animation, add one more line: -2 0 FAN.3 (For an example of a looping animation, see APPLE.PLY.) If you named this file FAN.PLY, then you could replay the images with the single command: PLAYBACK FAN.PLY The extension of '.PLY' is not mandatory, but future versions of PLAYBACK will probably use this extension as a default. Regarding memory usage: PLAYBACK requires enough free RAM to read ALL the disk images into memory before it starts to display any of them. If there is not enough free RAM, it exits with an error message and you see none of your animation. Following are some suggestions of what to do if you get this message: 1. Remove any large memory-resident (TSR) programs that you may have loaded. 2. If you have extended memory in your system, you may want to install the HIMEM.SYS extended memory manager (provided with the SURFMODL distribution disks), or a compatible memory manager like QEMM, Netroom, or 386-Max. New to version 3.0 is PLAYBACK's ability to store images in extended memory. Unfortunately, PLAYBACK animations are somewhat slower when using extended memory, due to the extra memory moving involved. Therefore, you will not see the smooth animations that are possible when only using standard RAM. 3. Edit the control file so there are not so many images in the animation. This will cut down on RAM usage, since RAM usage is proportional to the number of images. 4. You can re-run SURFINST and select a lower-resolution graphics mode, or one with fewer colors. If you have a VGA, you may even want to use one of the EGA modes or (gasp!) even a CGA mode. Of course, the pictures will not look as sharp but at least you can see the animation. USING REVOLUTION REVOLUTION provides a graphical interface to PREPROC, the SURFMODL preprocessor, for the generation of objects of revolution. It was written by Ian Murphy. This documentation should really be expanded on, but unfortunately I don't have time to do it more completely right now. If you find this documentation incomplete or inaccurate, I recommend you use the trial-and-error method. REVOLUTION is really quite easy to use, if you just play around with it a little. You start up the program by just typing REVOLUTE (if you have a CGA, EGA, Hercules, or Sanyo MBC-55x) or REVOLHZC (if you have a Heath/Zenith Z-100 or CGA that can't run the standard REVOLUTE file), or REVOLATT (if you have an AT&T 6300). There are no parameters on the command line. For all versions except REVOLATT, you will then select your system type from a menu. Next, you should immediately be placed on the graphics screen, with axes covering the screen and a small line segment and crosshair near the middle. If you have a system that supports text output on the graphics screen, then you will also see a line that looks like: Add Del Ins Move Redraw Params Write at the top of your screen. If your system doesn't support text on the graphics screen, then you had better write these commands down or you'll be lost when you start up REVOLUTION. The basic idea is to draw a picture on your screen of HALF of the object that you wish to create (remember, you can only create objects of revolution). The axis of rotation of the object is the vertical axis, and if you don't want a hole in your object you had better make sure that the first and last points of your picture lie on that axis. You move the crosshairs from one point to another on your lines using the left and right arrow keys. Note that this only moves you between the "major" points that you have created. Left arrow moves you in one direction and right arrow in the other. These directions are not really necessarily left and right; they are just backward and forward through the array of points you have drawn. To move one of these major points, hit the M key. If you receive the message to "select a point", then put the crosshair on the point you want to move and hit Enter. Otherwise, just hit your arrow keys and the current point will move. (If you don't have text capability on your graphics screen, you'll just have to tell by feeling your way around. If left and right arrow keys just move the crosshairs between points, then REVOLUTION is still waiting for you to select a point; if it moves your selected point left or right, then you are ready to go.) When you have moved the point where you want it, hit Enter and the point is kept at that place on the screen. The first letter of all the commands mentioned above is all you press to select a command in REVOLUTION. 'A' adds a new point, always after the "leftmost" point -- that's easier to see by trying it than by reading this documentation. 'I' inserts a new point between two old points, again to the "left" of the chosen point. 'D' deletes a point, and 'P' brings up a parameters menu to change several of the PREPROC inputs. See the PREPROC documentation for details. 'W' writes the data to a file. If you specify an extension to your filename, it is ignored; REVOLUTION files always end in an extension '.IN'. If (+%% '*ct a name like 'TEST' for your filename, then REVOLUTION will create two files: TEST.IN and TEST.BAT. The TEST.IN file is NOT a SURFMODL input file; it is a PREPROC input file. The easiest way to create a SURFMODL input file from this is to exit REVOLUTION (which you do by hitting the Escape key), and then type TEST. This runs the TEST.BAT file, which just contains the two lines: PREPROC test.IN test SURFMODL test [KVC 09/30/91 This should be modified to generate test.SRF, but this has not been done yet.] This just runs the TEST.IN file that REVOLUTION just created through PREPROC to create a SURFMODL data file called TEST, then starts up SURFMODL on that file. One other important note regarding REVOLUTION: the ordering of the major points. Since SURFMODL (and PREPROC) care about the ordering of nodes, some standard has to be set as to which node is the "first" one and which is the "last". In SURFMODL, this was done by the restriction that nodal connectivity is specified in a counter-clockwise direction when viewed from the outside of the surface. In REVOLUTION, in order to guarantee that nodes are generated properly for this rule, you have to follow some simple rules of ordering as well. This is easiest to explain with an example. If you imagine trying to create a sphere with REVOLUTION (by drawing a half-circle on the left side of the axis), the counter- clockwise rule is easy to apply if you just think of the "leftmost" point as the first one, and the "rightmost" point as the last. That means the leftmost point should be at the top of the screen, and the rightmost point at the bottom. In general, the rules are thus: (1) always draw your object on the left side of the axis; (2) always order the points counter- clockwise when proceeding from "left" to "right". You can violate these rules, and still get valid SURFMODL data files, but you may find your surfaces "inverted": SURFMODL shades the inside of the surface instead of the outside. Experiment with REVOLUTION, and I think you'll agree it's a valuable addition to the SURFMODL package. If you have problems with it, we apologize, but for now you'll just have to pour through the source code and figure it out yourself. This brings new meaning to the term "user- supported software"! Good luck! USING SURFEDIT SURFEDIT is designed to allow you to edit any SURFMODL data file, to make small changes to it graphically or merge multiple data files interactively. SURFEDIT was written by Ian Murphy, and really represents a valuable addition to the SURFMODL collection. However, like REVOLUTION, it needs some work. The file merging command, for instance, is buggy. You may often find your data points in the wrong position after merging two files. I ordinarily would not release such bug-ridden code, but SURFEDIT's primary purpose (graphically editing SURFMODL data files) works well and therefore (I think) makes it worthwhile nonetheless. If you need to merge multiple SURFMODL data files, your best bet for now is to use PREPROC. One more piece of bad news: SURFEDIT currently only works on EGA-compatible systems. Any other system will be hung by running SURFEDIT. You start the program by just typing SURFEDIT; any command line parameters are ignored. You will be asked for a file name, and you must specify the name of an existing SURFMODL data file (NOT a PREPROC data file). You must specify some file name here, since SURFEDIT cannot create a new one from scratch; it must have an old file to start from. Once SURFEDIT is started, you will be presented with three windows. These three windows always show the three principle orthogonal views of your object. In drafting terminology, the upper left view is called the "elevation"; the lower left is the "plan"; and the upper right is the "endview". These correspond to the X-Y, X-Z and Y-Z planes, respectively. You have eight commands available to you in SURFEDIT, which you specify by typing the first letter of the command: Z (Zoom), E (Edit), O (Options), R (Rotate), I (Import), T (Translate), M (Magnify), and W (Write). In addition, hitting the Escape key will exit the program, and hitting one of the arrow keys will allow you to "select" a different window. You always know the selected window because it is highlighted. At all times, one of the three windows is selected, and that is the one on which your commands will operate. An explanation of the term "object" is in order. In SURFEDIT, an "object" is defined by a file. The first data file you specify to be read in is thereafter referred to as object number 1. If you later "Import" a file, it is referred to as object number 2, the second file you Import is object number 3, and so on. (There is a limit of 10 objects in SURFEDIT.) In several of the commands, SURFEDIT will ask you what object you wish to refer to, so keep track of your object numbers. The Zoom command presents a rectangular box in the currently selected window. You may move this box anywhere inside the window, to specify an area to zoom in on. WARNING: This command uses the numbers on the numeric keypad, not real arrow keys! Therefore, you must have Num Lock ON when you issue this command. (For anyone who does not have the arrows printed on their numeric keypad, here is the translation: 8 is the up arrow, 2 is the down arrow, 4 is the left arrow, and 6 is the right arrow.) This is inconsistent with the way the rest of the program works, by the way. In any of the other commands in SURFEDIT, when the directions say to hit an arrow key it means a real arrow key (with Num Lock off). When you have positioned the box where you want to zoom, hit the Enter key to actually make it zoom in. The Edit command allows you to move selected nodes in one plane (the currently selected window). You are limited to the resolution of the graphics screen for the accuracy of your editing, but since this command also works on zoomed windows you actually have a great deal of control available. After hitting the 'E' key, you are presented with a crosshair. You move the crosshair near your desired node with the arrow keys, then hit Enter. The closest node to the crosshairs is selected, and the crosshairs reappear in their original position. Now move the crosshairs to the new place where you want to move the node, and hit Enter. You will not see the change reflected in the other two windows immediately, but it has been made internally. To see your editing changes in other windows, use the Options command, then hit 'R' for Reset. This redraws all three windows with the current data. It also resets any zooms to the initial drawing scales (the program automatically scales your object to fit within all three windows, with the same scale used in all windows). The Rotate command allows you to specify an angle (in degrees) to rotate an object about each of the three principle axes. The Import command allows you to read another SURFMODL data file, to merge it with the current data file. The Translate command allows you to specify a distance to be added to every coordinate in an object, along each of the three principle axes. Units used are real numbers (the same as the units you used originally to create the data file). The Magnify command allows you to scale an object in each of the three principle directions. A scale of 1 leaves the object unchanged in that direction. Note that Magnify is different than Zoom, because Zoom just allows you to enlarge the drawing of a view. Magnify actually changes the internal nodal coordinates of the object. Finally, the Write command allows you to specify a file name to save the current data into a SURFMODL data file. It does not exit the program; use the Escape key for that. PRINTING THE SCREEN SURFMODL does not provide an internal facility for printing a copy of the graphics screen; however it is fairly easy to do. If you have a CGA or EGA compatible graphics adapter and a printer that is compatible with the IBM dot matrix graphics printers (as many are, including the popular Epson printers), you can do screen dumps using the GRAPHICS.COM program that comes with MSDOS. Install it by typing GRAPHICS sometime before entering SURFMODL (or better yet, put it in your AUTOEXEC.BAT); then the <Shift>-<PrtSc> combination will copy the current screen to the printer, even in graphics mode. A better solution to the problem is to use Colour Snap, a shareware utility (which I did not write) that I am now including on the SURFMODL distribution disks in the SURFPRNT module. This supports a wide range of color printers (as well as black-and- white) and several graphics modes. Unfortunately, it does not presently support the 256-color VGA modes, although the author has told me he is working on this. See the documentation that came in the SURFPRNT module for details on its use, and write to the author if you want to find out as soon as the full VGA support is added. There are also several commercial TSR screen dump programs available, which you may want to consider. Several of them support many combinations of screen and printer, including laser printers and color support. The one I have used is called INSET, and is produced by Inset Systems Inc. (formerly the American Programmers Guild), 12 Mill Plain Road, Danbury CT 06811. Their telephone number is (203)794-0396. I believe I paid $129 for my copy, but that was in 1986 so prices have changed. INSET supports a large number of printers and adapters, and also has many other features for merging graphics with your text files, shrinking or enlarging images, changing aspect ratios, dithering and color support. I highly recommend it. I have no affiliation or financial interest in Inset Systems Inc. INSTRUCTIONS FOR RECOMPILING SURFMODL 3.00C Included on the SURFMODL distribution disks is a batch file, called COMPILE.BAT, which uses the TP line mode to compile the program. For many users, recompiling SURFMODL is as simple as executing COMPILE.BAT. There are, however, some options to consider. You can turn off support for the 80x87 floating point processor, control linking of .BGI files in the .EXE file, generation of debugging code, generation of shadow processing code, and generation of code for "external" graphics devices (the VAXmate and Commodore Amiga). Invoking any of these options is quite easy; you just edit the file DEFINES.INC, included on the distribution disks. Since DEFINES.INC is included at the beginning of all the programs and units of SURFMODL, a change in this file changes all the files at compilation time. In this file, you will also find comments explaining the meaning of each of the optional define statements. Read it for details. I should also mention that trying to compile SURFMODL exactly as it is supplied on the distribution diskettes will result in an error message. That is because the top line of DEFINES.INC is a comment that has not been commented out. It was done to purposely make you read that file before compiling. The minimum change you must make is to comment out the first few lines of the file. INTERPRETATION OF ERROR MESSAGES Following is a list of common error conditions found when running SURFMODL, and what to do about them: SYMPTOM: "ERROR: SURFMODL.CFG does not exist." ACTION: You are missing the SURFMODL.CFG file, which must be present either in the current directory or the one you keep all your data files in. If you keep data files somewhere other than the current directory, you should set an environment variable to point to it, as in: SET SURFDIR=C:\SURFMODL\DATA SYMPTOM: "Device driver file not found..." ACTION: You have tried to run SURFMODL without having the Borland Graphic Interface (BGI) file for your graphics adapter in the current directory. All the BGI files used by SURFMODL are provided on the SURFMODL release disks. Copy the one that corresponds to your adapter into your current directory before running SURFMODL. If you're not sure, just copy them all into the current directory. Another alternative is to set the environment variable BGIDIR, which SURFMODL checks upon startup. You can set this to hold the name of the directory in which you keep your BGI files, as in: SET BGIDIR=C:\TURBO\DRIVERS SYMPTOM: You hear a beep after hitting the 'F' key in SURFMODL (to try to save a copy of the current screen to a file), and there is no disk activity. ACTION: SURFMODL could not allocate enough memory to save the screen, or else you ran out of disk space. If you are sure you have plenty of disk space, you may be getting the beep simply because you do not have enough memory free during the run. SYMPTOM: "Could not allocate memory for bitmaps" (in PLAYBACK) ACTION: PLAYBACK loads all of the images into memory before starting to display them. Therefore, the more images you request to be played back, the more memory required. You will see this message for each file requested in your playback control file that cannot fit into memory. It is a non-fatal error; all images before the ones that exceeded your memory limits will be properly displayed. NOTE: PLAYBACK is capable of using extended memory to store the images for animation. To use this feature, you must have an extended memory manager (XMS) loaded, such as HIMEM.SYS, Quarterdeck's QEMM, or Qualita's 386MAX. HIMEM.SYS is provided on the SURFMODL distribution disks; just add this line to your CONFIG.SYS: DEVICE=HIMEM.SYS SYMPTOM: "Warning: Focal point outside data limits. Press any key..." ACTION: This is not really an error message; it is just a friendly warning by SURFMODL that the focal point is outside the limits of the object. If the resulting plot is nothing but a blank screen, it does not necessarily mean there is something wrong with your data; just that you picked a bad focal point. SYMPTOM: "Error: You have attempted to plot a concave surface" (etc.) ACTION: This message occurs because the arrays in the filled surface routine in SURFMODL had their dimension exceeded. Usually, this is only possible if you tried to plot a surface with concavities. If you are sure your surfaces are convex, the easiest way to make this message go away is to reduce the magnification factor of the plot. If you see this message often, then the constant MAXPTS in SURFMODL.PAS should be raised, and SURFMODL recompiled. SYMPTOM: In the wireframe plot, surfaces look more like "hourglasses" than quadrilaterals. ACTION: Your node numbers were not specified in an order to complete a circular path around the surface. For example, if your old node numbering was: 1,2,3,4 then try: 1,3,4,2 and your problem should be fixed. SYMPTOM: You notice that some surfaces are covering (or partially covering) surfaces that they should be behind. ACTION: This is usually caused by using surfaces with too high an aspect ratio - that is, they are much longer in one direction than in the other. (You may see this in my ROBOT2.SRF data file.) SYMPTOM: You notice surfaces are not being plotted when they should be. ACTION: You probably reversed the direction of the node numbering, and ordered them clockwise instead of counter-clockwise (when viewed from the visible side of the surface). (This is the case with the base of the robot in my ROBOT2.SRF data file.) One fix is to correct the numbering; another is to change NSIDES from 1 to 2. SURFMODL USER REGISTRATION As a low-cost way to communicate with SURFMODL users, I am making the following offer: If you mail me a self-addressed, stamped envelope (SASE), I will keep you informed of the latest developments in SURFMODL. If you are not from North America, you can instead send one International Postal Coupon and a self- addressed envelope. Please don't expect an immediate reply; I am only going to mail out notices when I have compiled enough material to make it worthwhile. You would be amazed at the number of people who have written to me, asking to be included on the mailing list, without including any postage. I don't ask for contributions or any other payment, so I really think this is a reasonable request in return for a promise to keep you up to date. I welcome you to send me copies of your data files for new and interesting objects that you display with SURFMODL, and I certainly welcome enhancements to SURFMODL or any of its support programs. If you don't stipulate otherwise, I will assume that any data files or programs you send me are intended for general distribution. I really look forward to seeing what other people can do. I have purposely avoided printing a "registration form" in the documentation, as is so popular, because I want to get a letter from you -- not just a form. Let me know what you think about SURFMODL, how you think it could be enhanced, and, most importantly, what you're using it for. I really enjoy hearing about other people's appplications. If you write to report bugs, please stipulate which version you are running, and on what type of computer/graphics board. UPGRADING SURFMODL If you want to keep up with the latest version of SURFMODL, first of all you have to register; that much is obvious. In addition, you will want to know how you can obtain a copy of the latest version of SURFMODL. In the past, I have sent my newest releases to a public domain sales company called MicroCom Systems, and encouraged people to go there for their diskettes. Now, unfortunately, MicroCom is no longer responding to my letters. I have sent them two SURFMODL updates without getting so much as a note verifying receipt. Therefore, I am dropping my recommendation to use them and will now start distributing SURFMODL myself on diskette. Although I will mail SURFMODL anywhere in the world, there are also a few other distribution sites for SURFMODL which may be more convenient for you. Check the file DISTRIB.DOC on the distribution disks, for an up-to-date listing of prices and other distribution sites. These are not commercial companies; they are just other SURFMODL users like yourself. Below is my present address. I prefer not to get too many phone calls, but if you feel you have something important that is too difficult to put down on paper (or you want to make a business proposition!), by all means give me a call. You can get my number from information. Kenneth Van Camp RD #1 Box 1255 East Stroudsburg, PA 18301 U.S.A.