Limit carve distance

components/renderers/cpp/src/carver.cu

 #include "carver.hpp"
 
+__device__ inline float depthErrorCoef(const ftl::rgbd::Camera &cam, float disps=1.0f) {
+	return disps / (cam.baseline*cam.fx);
+}
+
 // ==== Reverse Verify Result ==================================================
 
 __global__ void reverse_check_kernel(
@@ -17,9 +21,11 @@ __global__ void reverse_check_kernel(
 	if (x < 0 || x >= vintrin.width || y < 0 || y >= vintrin.height) return;
 
 	float d = depth_in[y*pitch4+x];
+
+	const float err_coef = 0.001f; //depthErrorCoef(ointrin);
 	
-	// FIXME: This is dangerous, need to check through alternates instead
-	while (true) {
+	int count = 10;  // Allow max 2cm of carving.
+	while (--count >= 0) {
 		float3 campos = transformR * vintrin.screenToCam(x,y,d);
 		int2 spos = ointrin.camToScreen<int2>(campos);
 		int ox = spos.x;
@@ -27,16 +33,21 @@ __global__ void reverse_check_kernel(
 
 		if (campos.z > 0.0f && ox >= 0 && ox < ointrin.width && oy >= 0 && oy < ointrin.height) {
 			float d2 = depth_original[oy*opitch4+ox];
-			if (!(d2 < ointrin.maxDepth && d2 - campos.z > d2*0.001f)) break;
+
+			// TODO: Threshold comes from depth error characteristics
+			// If the value is significantly further then carve. Depth error
+			// is not always easy to calculate, depends on source.
+			if (!(d2 < ointrin.maxDepth && d2 - campos.z > d2*d2*err_coef)) break;
 			d += 0.002f;
 		} else break;
 	}
 
-	depth_in[y*pitch4+x] = d;
+	// Too much carving means just outright remove the point.
+	depth_in[y*pitch4+x] = (count < 0) ? 0.0f : d;
 }
 
 void ftl::cuda::depth_carve(cv::cuda::GpuMat &depth_in, const cv::cuda::GpuMat &depth_original, const float4x4 &transformR, const ftl::rgbd::Camera &vintrin, const ftl::rgbd::Camera &ointrin, cudaStream_t stream) {
-	static constexpr int THREADS_X = 8;
+	static constexpr int THREADS_X = 16;
 	static constexpr int THREADS_Y = 8;
 
 	const dim3 gridSize((depth_in.cols + THREADS_X - 1)/THREADS_X, (depth_in.rows + THREADS_Y - 1)/THREADS_Y);