public static void Contacts(int particleIndex,
int colliderIndex,
float4 particlePosition,
quaternion particleOrientation,
float4 particleVelocity,
float4 particleRadii,
float deltaTime,
ref NativeArray <BIHNode> bihNodes,
ref NativeArray <Edge> edges,
ref NativeArray <float2> vertices,
EdgeMeshHeader header,
ref BurstAffineTransform colliderToSolver,
ref BurstColliderShape shape,
NativeQueue <BurstContact> .ParallelWriter contacts)
{
float4 colliderSpacePosition = colliderToSolver.InverseTransformPoint(particlePosition);
float4 colliderSpaceVel = colliderToSolver.InverseTransformVector(particleVelocity * deltaTime);
BurstAabb particleBounds = new BurstAabb(colliderSpacePosition,
colliderSpacePosition + colliderSpaceVel,
particleRadii.x / math.cmax(colliderToSolver.scale));
colliderSpacePosition *= colliderToSolver.scale;
BIHTraverse(particleIndex, colliderIndex,
colliderSpacePosition, particleOrientation, colliderSpaceVel, particleRadii, ref particleBounds,
0, ref bihNodes, ref edges, ref vertices, ref header, ref colliderToSolver, ref shape, contacts);
}
private static void BIHTraverse(int particleIndex,
int colliderIndex,
float4 particlePosition,
quaternion particleOrientation,
float4 particleVelocity,
float4 particleRadii,
ref BurstAabb particleBounds,
int nodeIndex,
ref NativeArray <BIHNode> bihNodes,
ref NativeArray <Edge> edges,
ref NativeArray <float2> vertices,
ref EdgeMeshHeader header,
ref BurstAffineTransform colliderToSolver,
ref BurstColliderShape shape,
NativeQueue <BurstContact> .ParallelWriter contacts)
{
var node = bihNodes[header.firstNode + nodeIndex];
// amount by which we should inflate aabbs:
float offset = shape.contactOffset + particleRadii.x;
if (node.firstChild >= 0)
{
// visit min node:
if (particleBounds.min[node.axis] - offset <= node.min)
{
BIHTraverse(particleIndex, colliderIndex,
particlePosition, particleOrientation, particleVelocity, particleRadii, ref particleBounds,
node.firstChild, ref bihNodes, ref edges, ref vertices, ref header,
ref colliderToSolver, ref shape, contacts);
}
// visit max node:
if (particleBounds.max[node.axis] + offset >= node.max)
{
BIHTraverse(particleIndex, colliderIndex,
particlePosition, particleOrientation, particleVelocity, particleRadii, ref particleBounds,
node.firstChild + 1, ref bihNodes, ref edges, ref vertices, ref header,
ref colliderToSolver, ref shape, contacts);
}
}
else
{
// precalculate inverse of velocity vector for ray/aabb intersections:
float4 invDir = math.rcp(particleVelocity);
// contacts against all triangles:
for (int i = node.start; i < node.start + node.count; ++i)
{
Edge t = edges[header.firstEdge + i];
float4 v1 = new float4(vertices[header.firstVertex + t.i1], 0, 0) * colliderToSolver.scale;
float4 v2 = new float4(vertices[header.firstVertex + t.i2], 0, 0) * colliderToSolver.scale;
BurstAabb aabb = new BurstAabb(v1, v2, 0.01f);
aabb.Expand(new float4(offset));
// only generate a contact if the particle trajectory intersects its inflated aabb:
if (aabb.IntersectsRay(particlePosition, invDir, true))
{
float4 point = BurstMath.NearestPointOnEdge(v1, v2, particlePosition);
float4 pointToTri = particlePosition - point;
float distance = math.length(pointToTri);
if (distance > BurstMath.epsilon)
{
BurstContact c = new BurstContact()
{
entityA = particleIndex,
entityB = colliderIndex,
point = colliderToSolver.TransformPointUnscaled(point),
normal = colliderToSolver.TransformDirection(pointToTri / distance),
};
c.distance = distance - (shape.contactOffset + BurstMath.EllipsoidRadius(c.normal, particleOrientation, particleRadii.xyz));
contacts.Enqueue(c);
}
}
}
}
}
