From e0384cbcb7a69c9f301acf0e9f5852dbe7a164f3 Mon Sep 17 00:00:00 2001
From: Jacco Bikker <bikker.j@gmail.com>
Date: Fri, 15 Nov 2024 17:08:57 +0100
Subject: [PATCH] Small bug fix in optimizer.

---
 tiny_bvh.h             |  9 +++++++--
 tiny_bvh_speedtest.cpp | 42 ++++++++++++++++++++++++++++--------------
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/tiny_bvh.h b/tiny_bvh.h
index 3002104..7926eae 100644
--- a/tiny_bvh.h
+++ b/tiny_bvh.h
@@ -91,7 +91,7 @@ THE SOFTWARE.
 // library version
 #define TINY_BVH_VERSION_MAJOR	0
 #define TINY_BVH_VERSION_MINOR	8
-#define TINY_BVH_VERSION_SUB	2
+#define TINY_BVH_VERSION_SUB	3
 
 // ============================================================================
 //
@@ -356,6 +356,10 @@ class BVH
 		BASIC_BVH8,			// Input for CWBVH. Obtained by converting WALD_32BYTE.
 		CWBVH				// Fastest GPU rendering. Obtained by converting BASIC_BVH8.
 	};
+	enum BuildFlags {
+		NONE = 0,			// Default building behavior (binned, SAH-driven).
+		FULLSPLIT = 1		// Split as far as possible, even when SAH doesn't agree.
+	};
 	struct BVHNode
 	{
 		// 'Traditional' 32-byte BVH node layout, as proposed by Ingo Wald.
@@ -537,6 +541,7 @@ class BVH
 	bool refittable = true;			// Refits are safe only if the tree has no spatial splits.
 	bool frag_min_flipped = false;	// AVX builders flip aabb min.
 	bool may_have_holes = false;	// Threaded builds and MergeLeafs produce BVHs with unused nodes.
+	BuildFlags buildFlag = NONE;	// Hint to the builder.
 	// keep track of allocated buffer size to avoid 
 	// repeated allocation during layout conversion.
 	unsigned allocatedBVHNodes = 0;
@@ -1872,7 +1877,7 @@ unsigned BVH::FindBestNewPosition( const unsigned Lid )
 void BVH::ReinsertNodeVerbose( const unsigned Lid, const unsigned Nid, const unsigned origin )
 {
 	unsigned Xbest = FindBestNewPosition( Lid );
-	if (verbose[Xbest].parent == 0) Xbest = origin;
+	if (Xbest == 0 || verbose[Xbest].parent == 0) Xbest = origin;
 	const unsigned X1 = verbose[Xbest].parent;
 	BVHNodeVerbose& N = verbose[Nid];
 	N.left = Xbest, N.right = Lid;
diff --git a/tiny_bvh_speedtest.cpp b/tiny_bvh_speedtest.cpp
index 15838a4..e94235d 100644
--- a/tiny_bvh_speedtest.cpp
+++ b/tiny_bvh_speedtest.cpp
@@ -25,7 +25,7 @@
 #define BUILD_REFERENCE
 #define BUILD_AVX
 #define BUILD_NEON
-#define BUILD_SBVH
+// #define BUILD_SBVH
 #define TRAVERSE_2WAY_ST
 #define TRAVERSE_ALT2WAY_ST
 #define TRAVERSE_SOA2WAY_ST
@@ -381,19 +381,33 @@ int main()
 
 	// trace all rays three times to estimate average performance
 	// - single core version, alternative bvh layout
-	printf( "Optimizing BVH... " );
-	t.reset();
-	bvh.Optimize( 1000000 );
-	bvh.Convert( BVH::WALD_32BYTE, BVH::ALT_SOA );
-	printf( "done (%.2fs). New: %i nodes, SAH=%.2f\n", t.elapsed(), bvh.NodeCount( BVH::WALD_32BYTE ), bvh.SAHCost() );
-	for (int i = 0; i < N; i += 2) bvh.Intersect( rays[i], BVH::ALT_SOA ); // re-warm
-	printf( "- CPU, coherent,   2-way optimized,    ST: " );
-	t.reset();
-	for (int pass = 0; pass < 3; pass++)
-		for (int i = 0; i < N; i++) bvh.Intersect( rays[i], BVH::ALT_SOA );
-	float traceTimeOpt = t.elapsed() / 3.0f;
-	mrays = (float)N / traceTimeOpt;
-	printf( "%8.1fms for %6.2fM rays => %6.2fMRay/s\n", traceTimeOpt * 1000, (float)N * 1e-6f, mrays * 1e-6f );
+	printf( "Optimizing BVH, regular...   " );
+	if (bvh.refittable)
+	{
+		printf( "Currently can't optimize SBVH.\n" );
+	}
+	else
+	{
+		t.reset();
+		bvh.Optimize( 1000000 );
+		printf( "done (%.2fs). New: %i nodes, SAH=%.2f\n", t.elapsed(), bvh.NodeCount( BVH::WALD_32BYTE ), bvh.SAHCost() );
+		printf( "Optimizing BVH, fullsplit... " );
+		t.reset();
+		bvh.buildFlag = BVH::FULLSPLIT;
+		bvh.Build( triangles, verts / 3 );
+		bvh.Optimize( 1000000 );
+		bvh.MergeLeafs();
+		printf( "done (%.2fs). New: %i nodes, SAH=%.2f\n", t.elapsed(), bvh.NodeCount( BVH::WALD_32BYTE ), bvh.SAHCost() );
+		bvh.Convert( BVH::WALD_32BYTE, BVH::ALT_SOA );
+		for (int i = 0; i < N; i += 2) bvh.Intersect( rays[i], BVH::ALT_SOA ); // re-warm
+		printf( "- CPU, coherent,   2-way optimized,    ST: " );
+		t.reset();
+		for (int pass = 0; pass < 3; pass++)
+			for (int i = 0; i < N; i++) bvh.Intersect( rays[i], BVH::ALT_SOA );
+		float traceTimeOpt = t.elapsed() / 3.0f;
+		mrays = (float)N / traceTimeOpt;
+		printf( "%8.1fms for %6.2fM rays => %6.2fMRay/s\n", traceTimeOpt * 1000, (float)N * 1e-6f, mrays * 1e-6f );
+	}
 
 #endif