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## AABB sweep collision detection problem

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### #1sublixt  Members

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Posted 29 March 2012 - 12:45 PM

I am having trouble trying to figure out aabb collision detection. I am trying converting the code from this tutorial (http://www.gamasutra...ames.php?page=3) to java/groovy but it doesnt work. I have checked through the code several times and I could not see any logic errors caused by translation. I was wondering if anyone could point out or suggest what might be wrong with it.

the main collision class with the problem that I am having.
//this class is made in groovy to take advantage of overloading constructors
public class Collision {
public static boolean collide(AABB first, AABB other, Float u0, Float u1){
//AABB class contains 3 vectors
//location - the x, y, z location
//extents - the extents of the bounding box
//sweep - the distance traveled that frame
Vector va = new Vector(first.sweep);
Vector vb = new Vector(other.sweep);

Vector v = vb - va;
Vector v0 = new Vector(0.0f, 0.0f, 0.0f);
Vector v1 = new Vector(1.0f, 1.0f, 1.0f);

if(overlap(first, other)){
u0 = 0.0f;
u1 = 0.0f;
return true;
}

for(int i = 0; i < 3; i++){
if(max(i, first) < min(i, other) && v[i] < 0)
v0[i] = (float)((max(i, first) - min(i, other) / v[i]));
else if(max(i, other) < min(i, first) && v[i] > 0)
v0[i] = (float)((min(i, first) - max(i, other)) / v[i]);

if(max(i, other) > min(i, first) && v[i] < 0)
v1[i] = (float)((min(i, first) - max(i, other)) / v[i]);
else if(max(i, first) < min(i, other) && v[i] > 0)
v1[i] = (float)((max(i, first) - min(i, other)) / v[i]);
}

u0 = Math.max(v0.x, Math.max(v0.y, v0.z));
u1 = Math.min(v1.x, Math.min(v1.y, v1.z));
return u0 <= u1;
}

private static boolean overlap(AABB first, AABB other) {
Vector T = other.location - first.location;

return Math.abs(T.x) <= (first.location.x + other.location.x) &&
Math.abs(T.y) <= (first.location.y + other.location.y) &&
Math.abs(T.z) <= (first.location.z + other.location.z);
}

private static float max(int i, AABB bla){
bla.location[i] + bla.bounds[i];
}

private static float min(int i, AABB bla){
bla.location[i];
}
}

the class that handels the vectors
it is a wraper class for vector3f letting me overload operators
class Vector extends Vector3f {
public Vector(float f, float g, float h) {
super(f, g, h);
}

public Vector(Vector3f a){
super(a);
}

public Vector plus(Vector other){
return new Vector((float) (x + other.x), (float) (y + other.y), (float) (z + other.z));
}

public Vector minus(Vector other){
return new Vector((float) (x - other.x), (float) (y - other.y), (float) (z - other.z));
}

public Float getAt(Integer i){
if(i > 2 || i < 0)
throw new IndexOutOfBoundsException("Vector index out of bounds");

switch(i){
case 0: return x;
case 1: return y;
case 2: return z;
}
}

public void putAt(Integer i, Float a){
if(i > 2 || i < 0)
throw new IndexOutOfBoundsException("Vector index out of bounds");

switch(i){
case 0: x = a; return;
case 1: y = a; return;
case 2: z = a; return;
}
}

public static Vector downcast(Vector3f down){
return new Vector(down.x, down.y, down.z);
}
}

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