add preliminary GPU ray cast (brute-force slow, only against sphere, allocates OpenCL buffers at every cast)

src/Bullet3OpenCL/Raycast/kernels/rayCastKernels.cl

@@ -0,0 +1,96 @@
+
+typedef struct
+{
+	float4 m_from;
+	float4 m_to;
+} b3RayInfo;
+
+typedef struct
+{
+		float m_hitFraction;
+		int	m_hitResult0;
+		int	m_hitResult1;
+		int	m_hitResult2;
+		float4	m_hitPoint;
+		float4	m_hitNormal;
+} b3RayHit;
+
+typedef struct
+{
+	float4 m_pos;
+	float4 m_quat;
+	float4 m_linVel;
+	float4 m_angVel;
+
+	unsigned int m_collidableIdx;
+	float m_invMass;
+	float m_restituitionCoeff;
+	float m_frictionCoeff;
+} Body;
+
+typedef struct Collidable
+{
+	int m_unused1;
+	int m_unused2;
+	int m_shapeType;
+	int m_shapeIndex;
+} Collidable;
+
+bool sphere_intersect(float4 spherePos,  float radius, float4 rayFrom, float4 rayTo)
+{
+    // rs = ray.org - sphere.center
+  float4 rs = rayFrom - spherePos;
+  rs.w = 0.f;
+	float4 rayDir = (rayTo-rayFrom);
+	rayDir.w = 0.f;
+	rayDir = normalize(rayDir);
+
+  float B = dot(rs, rayDir);
+  float C = dot(rs, rs) - (radius * radius);
+  float D = B * B - C;
+
+    if (D > 0.0)
+    {
+        float t = -B - sqrt(D);
+        if ( (t > 0.0))// && (t < isect.t) )
+        {
+            return true;//isect.t = t;
+		}
+	}
+	return false;
+}
+
+__kernel void rayCastKernel(  
+	int numRays, 
+	const __global b3RayInfo* rays, 
+	__global b3RayHit* hits, 
+	const int numBodies, 
+	__global Body* bodies,
+	__global Collidable* collidables)
+{
+
+	bool hit=false;
+
+	int i = get_global_id(0);
+	if (i<numRays)
+	{
+		hits[i].m_hitFraction = 1.f;
+
+		float4 rayFrom = rays[i].m_from;
+		float4 rayTo = rays[i].m_to;
+		
+		for (int b=0;b<numBodies;b++)
+		{
+					
+				float4 pos = bodies[b].m_pos;
+	//		float4 orn = bodies[b].m_quat;
+				
+				float radius = 1.f;
+	
+				if (sphere_intersect(pos,  radius, rayFrom, rayTo))
+					hit = true;
+		}
+		if (hit)
+					hits[i].m_hitFraction = 0.f;
+	}
+}