PLIB 1.8.5+ r2173 from http://plib.svn.sourceforge.net/svnroot/plib/trunk
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Alexander Deynichenko
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML>
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<HEAD>
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<META http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<TITLE>WELCOME TO S.I.M.O.N</TITLE>
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</HEAD>
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<BODY>
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<H1>WELCOME TO S.I.M.O.N</H1>
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<center>by Steve Baker</center>
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SIMON stands for:
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<pre>
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Simple
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Interface for
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Making
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Oliver's programs
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Nice.
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</pre>
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This is a simple set of functions that hide much of the nastiness
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of 3D programming to make it possible for someone with only the
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very minimum of programming experience to write simple 3D applications.
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<p>
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If you want something more complicated or with better features then
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don't complain about SIMON - just use raw PLIB (upon which SIMON is
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based).
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<H1>HOW TO WRITE YOUR PROGRAM.</H1>
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You have to write TWO C (or C++) functions:
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<pre>
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int main ()
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</pre>
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...and...
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<pre>
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void siUpdate ()
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</pre>
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The 'main' function has to load whatever 3D models the program needs
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and then call a function called 'siRun()'.
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<p>
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siRun does things like opening the 3D window, clearing the screen and
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drawing all of the models. When it's time to move the models around,
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it calls your function 'siUpdate'.
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<p>
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All SIMON programs have to start with the line:
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<pre>
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#include <simon.h>
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</pre>
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...this brings in all the information the compiler needs in order for you to
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write a SIMON program. Think of it like '#include <stdio.h>' but for
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programs that are just doing 3D rendering.
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<p>
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Then, you have to declare an integer variable for everything in the scene
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that your program needs - which includes at least the scenery and the camera.
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<p>
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For example:
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<pre>
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int camera ;
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int tux ;
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int scenery ;
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</pre>
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Next, you have your 'main' program - which loads up the models and then
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calls the 'siRun()' function and then exits.
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<pre>
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int main ()
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{
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scenery = siLoad ( "scenery.ac" ) ;
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tux = siLoad ( "tuxedo.ac" ) ;
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camera = 0 ;
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siRun () ;
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return 0 ;
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}
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</pre>
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The 'siLoad' function loads a 3D model and returns a number for
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that model that you can save into a variable. That number can be
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used to move the model around later on. The final part of this
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'loading' stage is to set the number for the 'camera'. In SIMON,
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the camera is always model number zero and you can't 'siLoad' a
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model for it or it won't work.
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<p>
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Then, you call 'siRun()' - which runs the entire update process. If
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'siRun' ever returns, you can just exit the program.
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<p>
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Now we have our scene all set up and ready to go - so the program
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will call your 'siUpdate' function to move the models (and the
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camera) around - and then draw the scene.
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<pre>
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int frameno = 0 ;
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void siUpdate ()
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{
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frameno = frameno + 1 ;
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siPosition ( tux , 0, 0, 0, frameno, 0, 0 ) ;
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siPosition ( camera, 0, -5, 1, 0, 0, 0 ) ;
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}
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</pre>
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Here we defined a simple variable called 'frameno' which is increased
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by one every time the 'siUpdate' function is called to give the program
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an idea of how much time has gone by.
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<p>
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Finally, we set the position of the camera and tux by calling
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'siPosition' for each of them.
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<p>
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'siPosition' is a function that needs SEVEN things to be passed to it.
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<ol>
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<li>The first is the variable that contains the number of the object you
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want to position.
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<li>The second is the X coordinate that you want that object to have
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(in Meters).
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<li>The third is the Y coordinate.
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<li>The fourth is the Z coordinate (the height).
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<li>The fifth is the 'heading' - which is the direction that the object
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is pointing. If you model your objects with their noses pointing
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North in the modeller then this number will be the angle in degrees
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measured in an anticlockwise direction from due North.
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<li>The sixth is the 'pitch' - which is the amount that the object is
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leaning backwards (in degrees).
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<li>The seventh (and last) is the 'roll' - which is the amount that the
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object is leaning sideways (also in degrees).
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</ol>
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That's a lot of information - but it's what you need to tell the
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object for it to know where to appear in the scene.
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<p>
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In our example program, we first had:
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<pre>
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siPosition ( tux, 0, 0, 0, frameno, 0, 0 ) ;
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</pre>
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...which puts Tux at X=0, Y=0, Z=0 (which is at the origin of the scene)
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and sets his 'heading' equal to this 'frameno' variable. Thus, as time
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goes on, and we keep adding one to 'frameno', Tux's heading number will
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gradually increase from zero upwards. This should cause him to rotate
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in place. Since pitch and roll are both zero, he'll be standing upright.
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<p>
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The slPosition command for the Camera:
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<pre>
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siPosition ( camera, 0, -5, 1, 0, 0, 0 ) ;
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</pre>
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...puts the camera at X=0, Y=-5, Z=1 - which is back 5 meters from where
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Tux is - and one meter up into the air. This should give us a nice view
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of him as he spins.
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<H1>READING THE JOYSTICK.</H1>
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These functions let you read the Left/Right and Up/Down axes of the
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joystick:
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<pre>
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leftright = siJoystickLR () ;
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updown = siJoystickUD () ;
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</pre>
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The numbers that this will put into the variables 'leftright' and
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'updown' range from -1.0 to +1.0. Leftwards and Upwards movements
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generate 1, Rightwards and Downwards movements generate -1, when the
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stick is in the middle you get zeroes.
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<p>
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To read the buttons, you can use these functions:
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<pre>
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buttonA = siJoystickA () ;
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buttonB = siJoystickB () ;
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buttonC = siJoystickC () ;
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buttonD = siJoystickD () ;
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buttonL = siJoystickL () ;
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buttonR = siJoystickR () ;
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</pre>
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...the variables should be 'int' varaibles and will be set to 1 if the
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button is pressed or 0 if it's not.
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<H1>OTHER MOVEMENT COMMANDS.</H1>
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Other commands let you set the Velocity for objects:
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<pre>
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siVelocity ( object, x, y, z, h, p, r ) ;
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</pre>
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...and set a speed and a direction:
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<pre>
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siSpeedAndDirection ( object, speed, heading, pitch ) ;
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</pre>
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...you can also get the current position for the object:
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<pre>
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x = siGetPositionX ( object ) ;
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y = siGetPositionY ( object ) ;
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z = siGetPositionZ ( object ) ;
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h = siGetPositionH ( object ) ;
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p = siGetPositionP ( object ) ;
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r = siGetPositionR ( object ) ;
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</pre>
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<H1>THE MAKEFILE.</H1>
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Once you start to have things like SIMON being used with your program,
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it can be quite a complicated process to compile your program. It's a
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lot of typing and you'll make lots of mistakes.
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<p>
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For that reason, Linux uses a command called 'make' to compile complicated
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programs according to some rules that you tell it in a special file that's
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called 'Makefile'. Once you have a 'Makefile' set up for your program,
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you only ever need to type 'make' in order to compile your program -
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no matter how complicated it gets to be.
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<p>
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A good 'Makefile' for a SIMON program would be:
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<pre>
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#
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# List the names of the programs we want to build here...
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#
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TARGETS = test1
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#======================== DON'T CHANGE THIS PART =============================
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#
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SIMONDIR = /usr/local/simon
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SIMON = -I${SIMONDIR} -L${SIMONDIR}
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LIBS = -lsimon -lplibssg -lplibsg -lplibul -lglut -lGLU -lGL -L/usr/X11/lib -lX11 -lm
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all: ${TARGETS}
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#=============================================================================
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#
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# Copy this for every program you want to write - changing 'test1'
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# to whatever your program is called.
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#
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test1 : test1.cxx ; g++ ${SIMON} -o test1 test1.cxx ${LIBS}
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</pre>
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</BODY>
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</HTML>
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