added OpenCL cloth demo, contributed by AMD.

updated GpuSoftBodySolvers
updated DirectCompute cloth demo

src/BulletMultiThreaded/GpuSoftBodySolvers/OpenCL/OpenCLC10/UpdateConstants.cl

@@ -0,0 +1,44 @@
+MSTRINGIFY(
+
+/*#define float3 float4
+
+float dot3(float3 a, float3 b)
+{
+   return a.x*b.x + a.y*b.y + a.z*b.z;
+}*/
+
+__kernel void 
+UpdateConstantsKernel( 
+	const int numLinks,
+	__global int2 * g_linksVertexIndices,
+	__global float4 * g_vertexPositions,
+	__global float * g_vertexInverseMasses,
+	__global float * g_linksMaterialLSC,
+	__global float * g_linksMassLSC,
+	__global float * g_linksRestLengthSquared,
+	__global float * g_linksRestLengths)
+{
+	int linkID = get_global_id(0);
+	if( linkID < numLinks )
+	{	
+		int2 nodeIndices = g_linksVertexIndices[linkID];
+		int node0 = nodeIndices.x;
+		int node1 = nodeIndices.y;
+		float linearStiffnessCoefficient = g_linksMaterialLSC[ linkID ];
+		
+		float3 position0   = g_vertexPositions[node0].xyz;
+		float3 position1   = g_vertexPositions[node1].xyz;
+		float inverseMass0 = g_vertexInverseMasses[node0];
+		float inverseMass1 = g_vertexInverseMasses[node1];
+
+		float3 difference = position0 - position1;
+		float length2 = dot(difference, difference);
+		float length = sqrt(length2);
+	
+		g_linksRestLengths[linkID] = length;
+		g_linksMassLSC[linkID] = (inverseMass0 + inverseMass1)/linearStiffnessCoefficient;
+		g_linksRestLengthSquared[linkID] = length*length;		
+	}
+}
+
+);