_xiaofang/xiaofang/Assets/Obi/Resources/Compute/BoxShape.compute

#include "ColliderDefinitions.cginc"
#include "ContactHandling.cginc"
#include "Transform.cginc"
#include "Simplex.cginc"
#include "Bounds.cginc"
#include "SolverParameters.cginc"
#include "Optimization.cginc"

#pragma kernel GenerateContacts

StructuredBuffer<float4> positions;
StructuredBuffer<quaternion> orientations;
StructuredBuffer<float4> principalRadii;
StructuredBuffer<float4> velocities;

StructuredBuffer<int> simplices;

StructuredBuffer<transform> transforms;
StructuredBuffer<shape> shapes;

StructuredBuffer<uint2> contactPairs;
StructuredBuffer<int> contactOffsetsPerType;

RWStructuredBuffer<contact> contacts;
RWStructuredBuffer<uint> dispatchBuffer;

StructuredBuffer<transform> worldToSolver;

uint maxContacts; 

struct Box : IDistanceFunction
{
    shape s;
    transform colliderToSolver;
    
    void Evaluate(in float4 pos, in float4 radii, in quaternion orientation, inout SurfacePoint projectedPoint)
    {
        float4 center = s.center * colliderToSolver.scale;
        float4 size = s.size * colliderToSolver.scale * 0.5f;

        // clamp the point to the surface of the box:
        float4 pnt = colliderToSolver.InverseTransformPointUnscaled(pos) - center;

        if (s.is2D())
            pnt[2] = 0;

        // get minimum distance for each axis:
        float4 distances = size - abs(pnt);

        if (distances.x >= 0 && distances.y >= 0 && distances.z >= 0)
        {
            projectedPoint.normal = float4(0,0,0,0);
            projectedPoint.pos = pnt;

            // find minimum distance in all three axes and the axis index:        
            if (distances.y < distances.x && distances.y < distances.z)
            {
                projectedPoint.normal[1] = sign(pnt[1]);
                projectedPoint.pos[1] = size[1] * projectedPoint.normal[1];
            }
            else if (distances.z < distances.x && distances.z < distances.y)
            {
                projectedPoint.normal[2] = sign(pnt[2]);
                projectedPoint.pos[2] = size[2] * projectedPoint.normal[2];
            }
            else
            {
                projectedPoint.normal[0] = sign(pnt[0]);
                projectedPoint.pos[0] = size[0] * projectedPoint.normal[0];
            }
        }
        else
        {
            projectedPoint.pos = clamp(pnt, -size, size);
            projectedPoint.normal = normalizesafe(pnt - projectedPoint.pos);
        }

        projectedPoint.pos = colliderToSolver.TransformPointUnscaled(projectedPoint.pos + center + projectedPoint.normal * s.contactOffset);
        projectedPoint.normal = colliderToSolver.TransformDirection(projectedPoint.normal);
        projectedPoint.bary = float4(1,0,0,0);
    }
};

[numthreads(128, 1, 1)]
void GenerateContacts (uint3 id : SV_DispatchThreadID) 
{
    uint i = id.x;

    // entry #11 in the dispatch buffer is the amount of pairs for the first shape type.
    if (i >= dispatchBuffer[11 + 4*BOX_SHAPE]) return; 
    
    uint count = contacts.IncrementCounter();
    if (count < maxContacts)
    {
        int firstPair = contactOffsetsPerType[BOX_SHAPE];
        int simplexIndex = contactPairs[firstPair + i].x;
        int colliderIndex = contactPairs[firstPair + i].y;

        contact c = (contact)0;

        Box boxShape;
        boxShape.colliderToSolver = worldToSolver[0].Multiply(transforms[colliderIndex]);
        boxShape.s = shapes[colliderIndex];

        int simplexSize;
        int simplexStart = GetSimplexStartAndSize(simplexIndex, simplexSize);

        float4 simplexBary = BarycenterForSimplexOfSize(simplexSize);
        float4 simplexPoint;

        SurfacePoint surfacePoint = Optimize(boxShape, positions, orientations, principalRadii,
                                             simplices, simplexStart, simplexSize, simplexBary, simplexPoint, surfaceCollisionIterations, surfaceCollisionTolerance);

        c.pointB = surfacePoint.pos;
        c.normal = surfacePoint.normal * boxShape.s.isInverted();
        c.pointA = simplexBary;
        c.bodyA = simplexIndex;
        c.bodyB = colliderIndex;

        contacts[count] = c;
        
        InterlockedMax(dispatchBuffer[0],(count + 1) / 128 + 1);
        InterlockedMax(dispatchBuffer[3], count + 1);
    }
}