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, 178 insertions, 0 deletions

diff --git a/intern/cycles/bvh/bvh_unaligned.cpp b/intern/cycles/bvh/bvh_unaligned.cpp
new file mode 100644
index 00000000000..a876c670914
--- /dev/null
+++ b/intern/cycles/bvh/bvh_unaligned.cpp
@@ -0,0 +1,178 @@
+/*
+ * 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.
+ */
+
+
+#include "bvh_unaligned.h"
+
+#include "mesh.h"
+#include "object.h"
+
+#include "bvh_binning.h"
+#include "bvh_params.h"
+
+#include "util_boundbox.h"
+#include "util_debug.h"
+#include "util_transform.h"
+
+CCL_NAMESPACE_BEGIN
+
+
+BVHUnaligned::BVHUnaligned(const vector<Object*>& objects)
+        : objects_(objects)
+{
+}
+
+Transform BVHUnaligned::compute_aligned_space(
+        const BVHObjectBinning& range,
+        const BVHReference *references) const
+{
+	for(int i = range.start(); i < range.end(); ++i) {
+		const BVHReference& ref = references[i];
+		Transform aligned_space;
+		/* Use first primitive which defines correct direction to define
+		 * the orientation space.
+		 */
+		if(compute_aligned_space(ref, &aligned_space)) {
+			return aligned_space;
+		}
+	}
+	return transform_identity();
+}
+
+Transform BVHUnaligned::compute_aligned_space(
+        const BVHRange& range,
+        const BVHReference *references) const
+{
+	for(int i = range.start(); i < range.end(); ++i) {
+		const BVHReference& ref = references[i];
+		Transform aligned_space;
+		/* Use first primitive which defines correct direction to define
+		 * the orientation space.
+		 */
+		if(compute_aligned_space(ref, &aligned_space)) {
+			return aligned_space;
+		}
+	}
+	return transform_identity();
+}
+
+bool BVHUnaligned::compute_aligned_space(const BVHReference& ref,
+                                         Transform *aligned_space) const
+{
+	const Object *object = objects_[ref.prim_object()];
+	const int packed_type = ref.prim_type();
+	const int type = (packed_type & PRIMITIVE_ALL);
+	if(type & PRIMITIVE_CURVE) {
+		const int curve_index = ref.prim_index();
+		const int segment = PRIMITIVE_UNPACK_SEGMENT(packed_type);
+		const Mesh *mesh = object->mesh;
+		const Mesh::Curve& curve = mesh->get_curve(curve_index);
+		const int key = curve.first_key + segment;
+		const float3 v1 = mesh->curve_keys[key],
+		             v2 = mesh->curve_keys[key + 1];
+		float length;
+		const float3 axis = normalize_len(v2 - v1, &length);
+		if(length > 1e-6f) {
+			*aligned_space = make_transform_frame(axis);
+			return true;
+		}
+	}
+	*aligned_space = transform_identity();
+	return false;
+}
+
+BoundBox BVHUnaligned::compute_aligned_prim_boundbox(
+        const BVHReference& prim,
+        const Transform& aligned_space) const
+{
+	BoundBox bounds = BoundBox::empty;
+	const Object *object = objects_[prim.prim_object()];
+	const int packed_type = prim.prim_type();
+	const int type = (packed_type & PRIMITIVE_ALL);
+	if(type & PRIMITIVE_CURVE) {
+		const int curve_index = prim.prim_index();
+		const int segment = PRIMITIVE_UNPACK_SEGMENT(packed_type);
+		const Mesh *mesh = object->mesh;
+		const Mesh::Curve& curve = mesh->get_curve(curve_index);
+		curve.bounds_grow(segment,
+		                  &mesh->curve_keys[0],
+		                  &mesh->curve_radius[0],
+		                  aligned_space,
+		                  bounds);
+	}
+	else {
+		bounds = prim.bounds().transformed(&aligned_space);
+	}
+	return bounds;
+}
+
+BoundBox BVHUnaligned::compute_aligned_boundbox(
+        const BVHObjectBinning& range,
+        const BVHReference *references,
+        const Transform& aligned_space,
+        BoundBox *cent_bounds) const
+{
+	BoundBox bounds = BoundBox::empty;
+	if(cent_bounds != NULL) {
+		*cent_bounds = BoundBox::empty;
+	}
+	for(int i = range.start(); i < range.end(); ++i) {
+		const BVHReference& ref = references[i];
+		BoundBox ref_bounds = compute_aligned_prim_boundbox(ref, aligned_space);
+		bounds.grow(ref_bounds);
+		if(cent_bounds != NULL) {
+			cent_bounds->grow(ref_bounds.center2());
+		}
+	}
+	return bounds;
+}
+
+BoundBox BVHUnaligned::compute_aligned_boundbox(
+        const BVHRange& range,
+        const BVHReference *references,
+        const Transform& aligned_space,
+        BoundBox *cent_bounds) const
+{
+	BoundBox bounds = BoundBox::empty;
+	if(cent_bounds != NULL) {
+		*cent_bounds = BoundBox::empty;
+	}
+	for(int i = range.start(); i < range.end(); ++i) {
+		const BVHReference& ref = references[i];
+		BoundBox ref_bounds = compute_aligned_prim_boundbox(ref, aligned_space);
+		bounds.grow(ref_bounds);
+		if(cent_bounds != NULL) {
+			cent_bounds->grow(ref_bounds.center2());
+		}
+	}
+	return bounds;
+}
+
+Transform BVHUnaligned::compute_node_transform(
+        const BoundBox& bounds,
+        const Transform& aligned_space)
+{
+	Transform space = aligned_space;
+	space.x.w -= bounds.min.x;
+	space.y.w -= bounds.min.y;
+	space.z.w -= bounds.min.z;
+	float3 dim = bounds.max - bounds.min;
+	return transform_scale(1.0f / max(1e-18f, dim.x),
+	                       1.0f / max(1e-18f, dim.y),
+	                       1.0f / max(1e-18f, dim.z)) * space;
+}
+
+CCL_NAMESPACE_END