This program draws 3-D graphs either as wire frames or colored solids with hidden lines eliminated. It requires a minimum of 512K of memory.
This is a shareware program copyright 1987 to George Trepal. It's OK to distribute this program for a very small fee but not to sell it. By "very small" I mean just enough to cover disk and mailing costs as with the disks put out by computer clubs, Amicus, and Fred Fish. If you enjoy this program please send me a contribution. For $20 I'll send you an advanced version of this program (in AmigaBASIC) that saves it's screens and lets you use your own equations. Also I'll tell you how to write your own good looking equations - there IS a trick to it. I'm George Trepal and I live at 2650 Alturas Road, Bartow, Florida 33830 (telephone 813-537-2521 evenings before 10 EST.)
SECTION 1:Demo
Load my program by clicking it's icon from Workbench. The computer will ask you to pick one of it's 35 equations. After you've chosen an equation the computer will suggest the numbers you could use. Tell the machine you're happy with these numbers by pressing Y for Yes. I'll tell you what's going on later but for now just demo the program.
When the screen clears and you hear the beep use the pulldown COMMANDS menu and select the "Go using 3-D opaque solid" option. The machine will draw a 3-D graph in glorious color in it's fastest (though not its best) plotting mode.
SECTION 2: Using the program
Using the same equation let's explore the pulldown menus.
The COMMANDS menu is:
GO using Xored wire frame
GO using 3D opaque solid
GO using Simple wire frame
GO using Colored wire frame
Invert image
Clear screen
Square cells
Triangular cells
QUIT - use another equation
The GO commands are the LAST options you want to use since they start the computer drawing.
Examining the Go commands from last to first the colored wire frame option gives the best results and is the slowest plotting mode. Plot over the graph you made to see how much nicer it looks.
The simple wire frame option plots the equation as if the cells were outlined by wires. The graph it produces is orange and completely transparent.
You already know about the 3D opaque solid mode. This mode is good for fast examinations of equations.
Use the Xored mode AFTER one of the other modes has plotted an equation. Sometimes it adds an interesting translucency to graphs and other times it just makes a mess.
The invert option flips the graph over in the computer's memory. Nothing changes on the screen until you use one of the GO commands. (For computers Y values increase as you go down the screen. In real math Y increases as you go up the page so inverting a graph standardizes it.)
The clear screen option is obvious. The screen doesn't automatically clear when you use a GO command. This let's you replot over an existing graph.
The square and triangular cell commands are also obvious. Square cells plot faster than triangular cells but usually give less definition.
The QUIT command gets you back to the start of the program so you can play with other equations.
The COLORING menu simply has Type one through three. There's no way to tell in advance which Type will give the nicest looking graph. I like the results I've gotten with Type 2 so the machine defaults to it. Try 'em all.
Technical note: Type 1 finds the difference of position for points on a cell's diagonal, Type 2 finds it for a horizontal side and Type 3 for a vertical. From these differences the machine can figure out a cell's tilt and spatial positioning. (The positioning information let's the machine know where to put shadows.) The tilt determines which color a cell will be.
The EFFECTS menu is:
Cycle colors
Orange wire frame
Black wire frame
Haze on/off
Backdrop on/off
Shadow on/off
Cycling colors in a graph may improve it. To stop the cycling press the left mouse button.
The next two options control the color of the wire frame if you've used a wire frame. The computer defaults to the more appropriate color so you may never use these options. You can change the frame color without replotting.
Haze enhances the 3-D effect. Turn off the haze and replot a graph to see what I mean.
The backdrop is the network of blue lines on the screen. You can turn them on or off without having to replot.
Shadows, like haze, enhance the 3-D effect. Turn them off and replot the graph to see what I mean.
The remaining menus are ABOUT, PARAMETERS, and STORAGE.
The ABOUT menu is yet another attempt to get you to send me money.
The PARAMETER menu tells you what the X and Y values you used were and what the minimum and maximum Z values are.
The STORAGE menu doesn't work in this version. For an AmigaBASIC version that saves and also contains other goodies send me $20. The screens are saved as IFF files which graphics programs like Deluxe Paint and Aegis Images can load.
SECTION 3: What's happening
The equation is plotted with X being horizontal, Y going into the screen, and Z being vertical. The machine will scale each axis separately so the final plot won't be to any one scale.
The default numbers the computer would like you to use define the corners of a square with its center at the point (0,0). The corners are (Low X, High Y), (High X, High Y), (High X, Low Y) and (Low X, Low Y). I like squares but you don't need to stick to them. Use whatever coordinates you want.
SECTION 4: Troubleshooting
There are certain things that absolutely won't work such as division by zero. If you tell the computer to do something illegal you'll get an error message for illegal function call, division by zero, or overflow. The computer will do it's best not to let an error mess up the graph. Just remember that if you get an error the graph is probably inaccurate.
You may be able to avoid some errors. The machine examines only a few points and you have an infinite number to work with. Perhaps your equation bombed with a range of 5 to -5. It might work with a range of 5.0001 to -5.0001. Don't give up without a fight.
SECTION 5: A final appeal for alms
Sending me money gets you some fine software and encourages me to to enhance this program. And I really could use the money.
I have two wives and a goldfish to support and if things get any tighter I'll have to leave my Amiga and seek honest work.
