I'm trying to implement this approach in C# for a 2D xna game. It currently works about 3/4 of the time. I was wondering if anyone would be kind enough to tell me if I'm on the right track, and to point me to helpful resources that would help me master (to a reasonable extent) collision detection.

Here is the method. I'm not sure that all the methods I've used are working completely, but I assume for now that they are. The objects are in world space.

Code: Select all

```
public bool generalGJK(BoundingVolume objA, BoundingVolume objB, Vector2 velA, Vector2 velB, out GJKOutputForm form)
{
maxIter = 1000;
Vector2 r = velB - velA; //r - this is my assumption based on obseving behavior of minkowski difference
//This is not an intersection test, for now. We can run an axis of separation if vel = 0 HERE later.
if (r.Length() == 0)
{
form.TOI = 2;
form.collisionNormal = Vector2.Zero;
return false;
}
float hitParam = 0; //lambda
Vector2 s = Vector2.Zero; //s, which is the origin I think...
Vector2 hitSpot = s; //x
Vector2 normal = Vector2.Zero; //n
Vector2 nOriginToHitSpot; //w
VoronoiSimplex simplex = new VoronoiSimplex(); //P
Vector2 convergingNormal; //V
Vector2 tempMinkVert;
float epsilon = float.Epsilon;
//epsilon *= epsilon;
GeometryUtilities.minkDiffSupportMap(objA, objB, Vector2.One, out tempMinkVert); //get arbitrary point in C (which I assume is the
//minkowski difference).
convergingNormal = hitSpot - tempMinkVert; //v = x − "arbitrary point in C"
while (Vector2.Dot(convergingNormal, convergingNormal) > epsilon && (maxIter--) > 0)
{
GeometryUtilities.minkDiffSupportMap(objA, objB, convergingNormal, out tempMinkVert); // p <- Sc(v). v is a normal of C at p
nOriginToHitSpot = hitSpot - tempMinkVert;
float VdotW = Vector2.Dot(nOriginToHitSpot, convergingNormal);
if (hitParam > 1.0f)
{
form.TOI = 2;
form.collisionNormal = Vector2.Zero;
return false;
}
if (VdotW > 0)
{
float VdotR = Vector2.Dot(r, convergingNormal);
if (VdotR >= -1.0f*epsilon)
{
form.TOI = 2;
form.collisionNormal = Vector2.Zero;
return false;
}
else
{
hitParam = hitParam - VdotW / VdotR;
hitSpot = s+hitSpot+hitParam * r;
normal = convergingNormal;
}
}
simplex.addVertex(new Vector3(tempMinkVert.X, tempMinkVert.Y, 0.0f));
simplex.resetUsedVerts();
//simplex.deformAccordingToHitParam(new Vector3(hitSpot.X, hitSpot.Y, 0.0f));
simplex.findClosestPointOnSimplexTo(Vector3.Zero);
convergingNormal.X = simplex.PointOfMinNorm.X;
convergingNormal.Y = simplex.PointOfMinNorm.Y;
simplex.reduceSimplex();
}
float time = hitParam;
if (time > 1)
{
form.TOI = 2;
form.collisionNormal = Vector2.Zero;
return false;
}
else
{
form.TOI = time;
form.collisionNormal = normal;
return true;
}
}
```

concubicycle