• Advertisement
Sign in to follow this  
  • entries
  • comments
  • views

for all to enjoy

Sign in to follow this  


I'm do some cleaning of my code while thinking up the way to link all my current objects. But this isn't really about that so much. It is about the code taking out because its now been rewritten somewhere else.

This is my code to find the time of collision for two spheres. It solves the time, then moves objects to that time. When the two are at that point, make a vector from the two centers. Apply that as the new direction vector for each object, reversing when needed. Normalizes them, and then moves them the remaining time. It also marks them as moved because I was getting some strange results at first so I took some precautions. Anyways:

void ObjectManager::CollideSS(DWORD ref1, DWORD ref2, float tcount)
Vector3 i1 = pIndex[ref1].internal;
Vector3 i2 = pIndex[ref2].internal;
Vector3 d1 = pIndex[ref1].direction;
Vector3 d2 = pIndex[ref2].direction;
float s1 = pIndex[ref1].scalar / (1.0f/tcount);
float s2 = pIndex[ref2].scalar / (1.0f/tcount);
Vector3 s = (d1 * s1) + (d2 * s2);
Vector3 e = i2 - i1;
float r = pIndex[ref1].radius + pIndex[ref2].radius;
float solve = ((e*s)*(e*s)) + (r*r) - (e*e);
if(solve < 0.0f)
return; // no collision, or collision at 0

float t = e*s - sqrt(solve);
// move internals to sync with t
// if solve == 0, then collision is at start.
// so (sN * t) == 0, the new vector will be
// calculated and moved for all of time
i1 += (d1 * (s1 * t));
i2 += (d2 * (s2 * t));

Vector3 D1 = i2 - i1; // vector from 1 to 2 at collision
Vector3 D2 (-D1); // exact oppisite for other sphere

d1 = -D1;
d2 = -D2;
d1 = Normalize3(d1);
d2 = Normalize3(d2);

// should prolly check for more collisins here, but oh well
// move the stuff the rest of the way

i1 += (d1 * (s1 * (1.0f - t)));
i2 += (d2 * (s2 * (1.0f - t)));
pIndex[ref1].internal = i1;
pIndex[ref2].internal = i2;
pIndex[ref1].direction = d1;
pIndex[ref2].direction = d2;
pIndex[ref1].moved = true;
pIndex[ref2].moved = true;



Here is it's daddy. It started as just testing to see if we were moving at the object. But it was my first attempt at collision tests, so its pretty ugly I bet. :) Anyways, it was pretty fast for me. So another Ctrl-X from my file:

Vector3 ObjectManager::TestObjectRay(DWORD thisref, FLOAT tick)
Vector3 d (0.0f,0.0f,0.0f);

Vector3 testing (pIndex[thisref].internal);
Vector3 testdir (pIndex[thisref].direction);
FLOAT testvel = pIndex[thisref].scalar / (1.0f/tick);
Vector3 versus;
Vector3 verdir;
FLOAT vervel;

for(DWORD testRef = 0;testRef < m_dwNumWorldObjects;testRef++)
if( (testRef != thisref) && pIndex[thisref].moved == false ) // dont test vs self
versus = pIndex[testRef].internal;
verdir = pIndex[testRef].direction;
vervel = pIndex[testRef].scalar / (1.0f/tick);
Vector3 plot = testdir*testvel;
Vector3 tothis = versus-testing; // vector from S1 to S2

// check to see if we are even close enough to
// hit this object in timeframe
// ran is the distance around ourself (thisref) to test for objects
// vst is the distance (if any) the 2nd object is moving
float ran = Vector3Mag(plot) + pIndex[thisref].radius + pIndex[testRef].radius;
Vector3 vst = vervel * verdir;

// if versus is moving, and has not been moved
if(vervel && pIndex[testRef].moved == false)
ran += Vector3Mag(vst); // throw in the versus movement

if(ran > Vector3Mag(tothis)) // traveling more than distance to test
// test of we are heading to this object
// dot product resulted in less than 0 = no
FLOAT resulted = Normalize3(plot)*Normalize3(tothis);
if(resulted >= 0.0f)
Vector3 t2 = testing + ( plot );
Vector3 v2 = versus + ( vst );
tothis = v2-t2;

if(Vector3Mag(tothis) < pIndex[testRef].radius + pIndex[thisref].radius)
if(pIndex[thisref].ColType == COL_SPHERE && pIndex[testRef].ColType == COL_SPHERE)
CollideSS(thisref, testRef, tick); // sphere on sphere collision
else if(pIndex[thisref].ColType == COL_SPHERE && pIndex[testRef].ColType == COL_PLANE)
CollideSP(thisref, testRef, tick); // sphere on plane collision

return d;

They both used the pIndex array. I could/should have kept going with this, because I was getting nice results. Now I'm redesigning stuff, and decided I really am shooting for a slightly more complicated scene (than pong).

So there is my gift to all of the people who have never seen collision code. It should be helpful for someone who does not know how to start the tests.

Blah blah back to work, I'll let you know if I find anything else juicy.
Sign in to follow this  


Recommended Comments

There are no comments to display.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Advertisement