// While Time Step Not Over
while (RestTime>ZERO) {
lamda=10000; // Initialize To Very Large Value
// For All The Balls Find Closest Intersection Between Balls And Planes / Cylinders
for (int i=0;i<NrOfBalls;i++) {
// Compute New Position And Distance
OldPos[i]=ArrayPos[i];
TVector::unit(ArrayVel[i],uveloc);
ArrayPos[i]=ArrayPos[i]+ArrayVel[i]*RestTime;
rt2=OldPos[i].dist(ArrayPos[i]);
// Test If Collision Occured Between Ball And All 5 Planes
if (TestIntersionPlane(pl1,OldPos[i],uveloc,rt,norm)) {
// Find Intersection Time
rt4=rt*RestTime/rt2;
// If Smaller Than The One Already Stored Replace In Timestep
if (rt4<=lamda) {
// If Intersection Time In Current Time Step
if (rt4<=RestTime+ZERO) if (! ((rt<=ZERO)&&(uveloc.dot(norm)>ZERO)) ) {
normal=norm;
point=OldPos[i]+uveloc*rt;
lamda=rt4;
BallNr=i;
}
}
}
if (TestIntersionPlane(pl2, OldPos[i], uveloc, rt, norm)) {
// …The Same As Above Omitted For Space Reasons
}
if (TestIntersionPlane(pl3, OldPos[i], uveloc, rt, norm)) {
// …The Same As Above Omitted For Space Reasons
}
if (TestIntersionPlane(pl4, OldPos[i], uveloc, rt, norm)) {
// …The Same As Above Omitted For Space Reasons
}
if (TestIntersionPlane(pl5, OldPos[i], uveloc, rt, norm)) {
// …The Same As Above Omitted For Space Reasons
}
// Now Test Intersection With The 3 Cylinders
if (TestIntersionCylinder(cyl1, OldPos[i], uveloc, rt, norm, Nc)) {
rt4 = rt*RestTime/rt2;
if (rt4<=lamda) {
if (rt4<=RestTime+ZERO) if (! ((rt<=ZERO)&&(uveloc.dot(norm)>ZERO)) ) {
normal=norm;
point=Nc;
lamda=rt4;
BallNr=i;
}
}
}
if (TestIntersionCylinder(cyl2, OldPos[i], uveloc, rt, norm, Nc)) {
// …The Same As Above Omitted For Space Reasons
}
if (TestIntersionCylinder(cyl3, OldPos[i], uveloc, rt, norm, Nc)) {
// …The Same As Above Omitted For Space Reasons
}
}
// After All Balls Were Tested With Planes / Cylinders Test For Collision
// Between Them And Replace If Collision Time Smaller
if (FindBallCol(Pos2, BallTime, RestTime, BallColNr1, BallColNr2)) {
if (sounds) PlaySound("Explode.wav", NULL, SND_FILENAME|SND_ASYNC);
if ((lamda==10000) || (lamda>BallTime)) {
RestTime=RestTime-BallTime;
TVector pb1, pb2, xaxis, U1x, U1y, U2x, U2y, V1x, V1y, V2x, V2y;
double a,b;
…
Code Omitted For Space Reasons
The Code Is Described In The Physically Based Modeling Section Under Sphere To Sphere Collision
…
//Update Explosion Array And Insert Explosion
for(j=0; j<20; j++) {
if (ExplosionArray[j]._Alpha<=0) {
ExplosionArray[j]._Alpha=1;
ExplosionArray[j]._Position=ArrayPos[BallColNr1];
ExplosionArray[j]._Scale=1;
break;
}
}
continue;
}
}
// End Of Tests
// If Collision Occured Move Simulation For The Correct Timestep
// And Compute Response For The Colliding Ball
if (lamda != 10000) {
RestTime-=lamda;
for (j=0; j<NrOfBalls; j++) ArrayPos[j]=OldPos[j]+ArrayVel[j]*lamda;
rt2=ArrayVel[BallNr].mag();
ArrayVel[BallNr].unit();
ArrayVel[BallNr] = TVector::unit( (normal*(2*normal.dot(-ArrayVel[BallNr]))) + ArrayVel[BallNr] );
ArrayVel[BallNr] = ArrayVel[BallNr]*rt2;
// Update Explosion Array And Insert Explosion
for(j=0; j<20; j++) {
if (ExplosionArray[j]._Alpha<=0) {
ExplosionArray[j]._Alpha=1;
ExplosionArray[j]._Position=point;
ExplosionArray[j]._Scale=1;
break;
}
}
} else RestTime=0;
} // End Of While Loop
The Main Global Variables Of Importance Are:
| Represent the direction and position of the camera. The camera is moved using the LookAt function. As you will probably notice, if not in hook mode (which I will explain later), the whole scene rotates around, the degree of rotation is handled with camera_rotation. | TVector dir TVector pos(0,-50,1000); float camera_rotation=0; |
| Represent the acceleration applied to the moving balls. Acts as gravity in the application. | TVector accel(0,-0.05,0); |
| Arrays which hold the New and old ball positions and the velocity vector of each ball. The number of balls is hard coded to 10. | TVector ArrayVel[10]; TVector ArrayPos[10]; TVector OldPos[10]; int NrOfBalls=3; |
| The time step we use. | double Time=0.6; |
| If 1 the camera view changes and a (the ball with index 0 in the array) ball is followed. For making the camera following the ball we used its position and velocity vector to position the camera exactly behind the ball and make it look along the velocity vector of the ball. | int hook_toball1=0; |
| Self explanatory structures for holding data about explosions, planes and cylinders. | struct Plane struct Cylinder struct Explosion |
| The explosions are stored in a array, of fixed length. | Explosion ExplosionArray[20]; |
The Main Functions Of Interest Are:
| Perform Intersection tests with primitives | int TestIntersionPlane(…); int TestIntersionCylinder(…); |
| Loads Textures from bmp files | void LoadGLTextures(); |
| Has the rendering code. Renders the balls, walls, columns and explosions | void DrawGLScene(); |
| Performs the main simulation logic | void idle(); |
| Sets Up OpenGL state | void InitGL(); |
| Find if any balls collide again each other in current time step | int FindBallCol(…); |