MacFormat 1995 March/macformat-022.iso/Shareware City/Graphics/SPD/README.1st

Text File | 1994-10-28 | 10.2 KB | 227 lines | [TEXT/ttxt]

SPD 3.4 - October 29 1994
-------------------------------

by Alexander Enzmann, w/modifications and additions by Eric Haines

This is an updated version (a) of the Standard Procedural Databases (SPD v3.1)
package & library code distributed by Eric Haines.  In addition to supporting
the NFF object data format, the file "lib.c" has been extended to support the
input format of the following renderers:

    MTV (i.e. NFF)
    POV-Ray 1.0
    POV-Ray 2.0 [subject to change, though]
    Polyray 1.4 to 1.6
    Vivid 2.0
    QRT 1.5
    Rayshade 4.0.6
    RTrace 8.0.0
    Art 2.3 (from Vort)
    RenderMan RIB
    AutoCAD DXF [object data only]

    In addition, there is a program nff2rad.c which converts NFF data to
Radiance format (if anyone feels like folding this code into lib.c, please
do).  Note that this converter is not listed in the makefile since it's
special purpose (and standalone, so it's trivial to compile).

    There is also an obj2nff.awk awk script which converts Wavefront OBJ
files to NFF format.

    A very rudimentary capability to dump polygons in the PLG format used
by REND386 is also supported.  A very simple DXF reader has also been added.
Its primary purpose was to display simple DXF files to the screen, but it has
the side effect of being able to translate DXF files (only 3DFACE, though)
to any of the above ray tracer file formats.

    Simple display drivers have been included various flavors for the IBM
PC (VGA, Zortech, Gnu C, etc), Apple Macintosh, and Hewlett Packard Starbase.
Drivers are very simple to write:  you just need a display initialization
routine, a display close routine, and a line drawing routine.  For Unix
systems, for example, just copy and fill in unix.c.

    Feel free to play with this stuff in whatever manner you choose.  Eric
was kind enough to make the original freely available, and I'm not about to
change that.  Of course this code is provided without any warranty of any
kind, and no assumption of responsibility for any consequences of using it are
made.


Changes From Original
---------------------

The biggest changes to the original NFF/SPD stuff is in the area of surface
shading attributes.  Since many raytracers support scale values for more
components of the shading model than are present in NFF, these have been
added.  The new components that have to be given in any call to
"lib_output_color" are:  Ka (ambient), Shine (Phong specular), Shine angle
(50% falloff angle for Phong spot, in degrees).

The separation of the Phong values from the Ks (specular) value simply
reflects the fact that most renderers don't force you to do both at the same
time (RTrace being an exception).  Using a falloff angle for the Phong
highlight may seem odd to you, but it really is sensible.  Smaller angles mean
smaller highlights.

Another change in the call to "lib_output_color" is a parameter that allows
the definition of a texture name.  Many raytracers support named textures, by
using a non-NULL string, you can specify a predefined texture name (these
things are pretty renderer specific).  All of the examples use NULL, which
defaults to plopping the current color into each primitive.


Other stuff
-----------

The original documents have been included (unchanged).  As far as the
documents for each of the raytracers mentioned above, you will have to get
them from their source.  Most of those raytracers are available on Compuserve
(go GRAPHDEV).  I haven't included one with this library.

The database generation programs that were supplied with the original SPD
package have been altered slightly to accept values from the command line.
This makes it a little easier to generate outputs of varying complexity, and
for the various renderers.  Typically the order of the command line options
is:

    prog [-s size_factor] [-r renderer] [-c|-t]

i.e. "balls -s 2 -r 1 > balls.nff" generates a level 2 sphereflake in MTV's
native format (NFF).  The meaning of "size_factor" varies from program to
program, but basically indicates the complexity of the database that will be
generated.  The "renderer" option corresponds to the definitions in "def.h"
for the various supported renderers.  (i.e. 0 means display on screen, 2
means POV-Ray 1.0, ...)  The [-c|-t] determines the output format, -c means
output curved object primitives, -t means output polygonal patches in a mesh
for curved surfaces.  By default NFF is output, though this is easily changed
by changing OUTPUT_RT_DEFAULT in the code.  Also, typing "prog -?" gives you
the options available.

The DXF displayer/converter "showdxf" works as follows:

    showdxf [-r renderer] filename

"-r 0" means display on screen, the others convert, etc.  Two sample models,
skull.dxf and f117.dxf, are provided as examples.  These were created with the
HyperSpace(tm) 3-D digitizing system from Mira Imaging, Inc.  Contact them at
801-466-4641 (Seth Jarvis) for more information.

I've tried to comment to a reasonable extent, but to be sure, you will need to
be reasonably fluent in "C" to make full use of this stuff.  (Or perhaps make
bindings for Pascal & then just use as a library.)

Depending on the features or speed of a particular renderer, you can tell the
library code to output primitives in its native format.  The "sample.c" file
has a simple scene, which can now be output in any supported format.  I have
found this code to be very useful for generating frames for animations from
"C" programs.  All you need to do is open a file for output, generate the
database, and then use a "system" call to perform the render.  There are two
other sample procedural model generation files, "lattice.c" and "shells.c".

In addition to the sphere, polygon, and cylinder/cone objects that were
supported in the original SPD, support has been added for:  boxes, tori,
height fields, and superquadrics.  For those raytracers that do not support
these as primitives, the output will be a large number of triangle patches.

As far as video output goes, a couple of simple display driver files are
included:  "mac.c", "ibm.c", "hp.c", "disp.c".  These are enough to make
things work, but aren't meant to do much more than that.  If you wish to add a
new display engine for a new machine type not mentioned here, you will need to
create a new file and define the following functions:  display_init,
display_close, display_clear, display_plot [actually, currently not used], and
display_line [which is a little peculiar, see unix.c for details].  There is
also a routine kbhit() for allowing display interrupt from the keyboard, if
needed.  If you don't have access to display drivers for your machine, simply
compile with "unix.c" - all display calls will then be ignored.

Oh, yeah - the coordinate system used in this library is left-handed.  This
may seem backwards for those of you used to one renderer vs another, but it is
simple enough to change:  always negate the value of just one of the
coordinates and you get right-handed coordinates.

(Try "gears" for a real CPU eater)

If you wish to reach the people who tweaked this stuff, we are on Compuserve
(E-Mail, or in the GRAPHDEV forum) as:

Alexander Enzmann
  CIS: 70323,2461
  internet: [e-mail]

Eduard Schwan
  CIS: 71513,2161
  AppleLink: JL.MacTech
  internet: [e-mail]

The original author, Eric Haines, is at [e-mail].


Post-it Notes
-------------

   - POV-Ray does not support arbitrary polygons, you get lots of triangles
   - RTrace does not support Phong highlights separately from reflections. It
     is difficult to get RTrace surfaces to look like other renderers
   - Polygons in PLG format will typically need to be scaled way up.
   - Rayshade if compiled right out of the box won't take CR/LF pairs in files,
     end of lines must be a single LF.
   - QRT has bad refraction code and doesn't support arbitrary polygons
   - The Macintosh programs require at least System 6.0.4, and run just
     fine under System 7 & 7.1.  They also need a 68020 CPU, but do not
     require an FPU.  And for some of the larger runs, they may need 2 or
     3 mb of application heap space.  So they should run fine on LCs and
     powerbooks, given enough RAM and disk space!

History
--------

Sept. 6th release:
  Antonio Costa [[e-mail]]:
   - Added support for IBM PC DJGPP (GNU C) with GRX graphics [drv_ibm.c]
     and its makefile [makefile.dj] -- requires DJGPP graphic drivers
     *.GRD or *.GRN -- allows high resolutions and is fast!
   - Added EPSILON2 to defs.h because of precision problems (EPSILON is too
     small) and changed lib.c to use EPSILON2.
   - Added my own NFF generator: lattice -- creates a cubic lattice of
     reflective spheres connected by matte cylinders (big CPU eater!)
  Eric Haines [[e-mail]]:
   - Added shells.c, new procedural database generator (potential CPU eater)
   - Added more PLATFORM_MULTITASK() calls.
   - Added lib_open/lib_close calls (for easier maintenance and extension).

Sept. 8th release:
  Antonio Costa [[e-mail]]:
   - Corrected problem in lib_open/lib_close
   - Corrected filenames for MAC version (*.out) of many generators
   - Changed some things in shells.c (shells_get_opts and light source)

Feb 10 1994 release:
  Eduard Schwan [[e-mail]]:
   - Added ReadNFF generator
   - Renamed ShowDXF to ReadDXF, sounded more accurate (ReadOBJ in the works)
   - Broke the giant lib.c file into several smaller libXXX.c files.  The
     Mac Symantec compiler segments code on a per-file basis & lib.c was big
     enough to force an unwanted large-model compile.
   - Added a lib_output_comment routine in libprm.c, which lets you insert
     general comment strings into the data stream in the appropriate dialect.

June 1 1994 SPD 3.3f2 release:
   - Added RIB file output
   - Added DXF file output
   - Split lib_get_opts to generator and reader specific command line
     interpreters.
   - More breakup of the lib*.c files to make Mac happy.

August 7 1994 SPD 3.3f4 release:
   - Fixed bug in Teapot that stomped the dialog display.
   - Changed code to use standard system palette for screen display, so that
      it no longer goofs up Finder colors upon exit
   - Fixed "In Progress" dialog to refresh if switched out and back in.

October 22 1994 SPD 3.3f5 release:
   - Fixed problems in RIB output (updates sent from Eric Haines).

October 29 1994 SPD 3.4 release:
   - Final touches, changed version # to 3.4 per Eric's request.