Cycles: Implement unaligned nodes BVH builder

This is a special builder type which is allowed to orient nodes to
strands direction, hence minimizing their surface area in comparison
with axis-aligned nodes. Such nodes are much more efficient for hair
rendering.

Implementation of BVH builder is based on Embree, and generally idea
there is to calculate axis-aligned SAH and oriented SAH and if SAH
of oriented node is smaller than axis-aligned SAH we create unaligned
node.

We store both aligned and unaligned nodes in the same tree (which
seems to be different from what Embree is doing) so we don't have
any any extra calculations needed to set up hair ray for BVH
traversal, hence avoiding any possible negative effect of this new
BVH nodes type.

This new builder is currently not in use, still need to make BVH
traversal code aware of unaligned nodes.

1 files changed, 81 insertions, 0 deletions

diff --git a/intern/cycles/bvh/bvh_unaligned.h b/intern/cycles/bvh/bvh_unaligned.h
new file mode 100644
index 00000000000..4d0872f4a39
--- /dev/null
+++ b/intern/cycles/bvh/bvh_unaligned.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2011-2016 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __BVH_UNALIGNED_H__
+#define __BVH_UNALIGNED_H__
+
+#include "util_vector.h"
+
+CCL_NAMESPACE_BEGIN
+
+class BoundBox;
+class BVHObjectBinning;
+class BVHRange;
+class BVHReference;
+struct Transform;
+class Object;
+
+/* Helper class to perform calculations needed for unaligned nodes. */
+class BVHUnaligned {
+public:
+	BVHUnaligned(const vector<Object*>& objects);
+
+	/* Calculate alignment for the oriented node for a given range. */
+	Transform compute_aligned_space(
+	        const BVHObjectBinning& range,
+	        const BVHReference *references) const;
+	Transform compute_aligned_space(
+	        const BVHRange& range,
+	        const BVHReference *references) const;
+
+	/* Calculate alignment for the oriented node for a given reference.
+	 *
+	 * Return true when space was calculated successfully.
+	 */
+	bool compute_aligned_space(const BVHReference& ref,
+	                           Transform *aligned_space) const;
+
+	/* Calculate primitive's bounding box in given space. */
+	BoundBox compute_aligned_prim_boundbox(
+	        const BVHReference& prim,
+	        const Transform& aligned_space) const;
+
+	/* Calculate bounding box in given space. */
+	BoundBox compute_aligned_boundbox(
+	        const BVHObjectBinning& range,
+	        const BVHReference *references,
+	        const Transform& aligned_space,
+	        BoundBox *cent_bounds = NULL) const;
+	BoundBox compute_aligned_boundbox(
+	        const BVHRange& range,
+	        const BVHReference *references,
+	        const Transform& aligned_space,
+	        BoundBox *cent_bounds = NULL) const;
+
+	/* Calculate affine transform for node packing.
+	 * Bounds will be in the range of 0..1.
+	 */
+	static Transform compute_node_transform(const BoundBox& bounds,
+	                                        const Transform& aligned_space);
+protected:
+	/* List of objects BVH is being created for. */
+	const vector<Object*>& objects_;
+};
+
+CCL_NAMESPACE_END
+
+#endif /* __BVH_UNALIGNED_H__ */
+