Merge pull request #138 from romainaugier/main

Found a bug in BVH8_CPU CombineLeafs when number of triangles in BLAS…

tiny_bvh.h

@@ -2293,6 +2293,8 @@ void BVH::Refit( const uint32_t /* unused */ )
 	aabbMin = bvhNode[0].aabbMin, aabbMax = bvhNode[0].aabbMax;
 }
 
+#define FIX_COMBINE_LEAFS 1
+
 // CombineLeafs: Collapse subtrees if the summed leaf prim count does not
 // exceed the specified number. For BVH8_CPU construction.
 void BVH::CombineLeafs( const uint32_t primCount )
@@ -2317,8 +2319,13 @@ void BVH::CombineLeafs( const uint32_t primCount )
 			}
 			else
 			{
+#if FIX_COMBINE_LEAFS 
+				if (!left.isLeaf() && left.SurfaceArea() > 0) stack[stackPtr++] = node.leftFirst;
+				if (!right.isLeaf() && right.SurfaceArea() > 0) stack[stackPtr++] = node.leftFirst + 1;
+#else
 				if (!left.isLeaf()) stack[stackPtr++] = node.leftFirst;
 				if (!right.isLeaf()) stack[stackPtr++] = node.leftFirst + 1;
+#endif
 			}
 		}
 	}

tiny_bvh_minimal_bvh8_bug.cpp

@@ -0,0 +1,56 @@
+// Minimal example for tiny_bvh.h
+
+#define TINYBVH_IMPLEMENTATION
+#include "tiny_bvh.h"
+
+#include <cstdlib>
+#include <cstdio>
+
+#define TRIANGLE_COUNT 3
+
+tinybvh::bvhvec4 triangles[TRIANGLE_COUNT * 3]; // must be 16 byte!
+
+float uniform_rand() { return (float)rand() / (float)RAND_MAX; }
+
+int main()
+{
+	// create a scene consisting of some random small triangles
+	for (int i = 0; i < TRIANGLE_COUNT; i++)
+	{
+		// create a random triangle
+		tinybvh::bvhvec4& v0 = triangles[i * 3 + 0];
+		tinybvh::bvhvec4& v1 = triangles[i * 3 + 1];
+		tinybvh::bvhvec4& v2 = triangles[i * 3 + 2];
+		// triangle position, x/y/z = 0..1
+		float x = uniform_rand();
+		float y = uniform_rand();
+		float z = uniform_rand();
+		// set first vertex
+		v0.x = x + 0.1f * uniform_rand();
+		v0.y = y + 0.1f * uniform_rand();
+		v0.z = z + 0.1f * uniform_rand();
+		// set second vertex
+		v1.x = x + 0.1f * uniform_rand();
+		v1.y = y + 0.1f * uniform_rand();
+		v1.z = z + 0.1f * uniform_rand();
+		// set third vertex
+		v2.x = x + 0.1f * uniform_rand();
+		v2.y = y + 0.1f * uniform_rand();
+		v2.z = z + 0.1f * uniform_rand();
+	}
+
+	tinybvh::bvhvec3 O( 0.5f, 0.5f, -1 );
+	tinybvh::bvhvec3 D( 0.1f, 0, 2 );
+	tinybvh::Ray ray( O, D );
+
+	// build a BVH over the scene
+	tinybvh::BVH8_CPU bvh;
+	bvh.Build( triangles, TRIANGLE_COUNT );
+
+	// from here: play with the BVH!
+	int steps = bvh.Intersect( ray );
+	printf( "std: nearest intersection: %f (found in %i traversal steps).\n", ray.hit.t, steps );
+
+	// all done.
+	return 0;
+}