b03e66e75f
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.
255 lines
8.0 KiB
C++
255 lines
8.0 KiB
C++
/*
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* Adapted from code copyright 2009-2011 Intel Corporation
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* Modifications Copyright 2012, Blender Foundation.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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//#define __KERNEL_SSE__
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#include <stdlib.h>
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#include "bvh_binning.h"
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#include "util_algorithm.h"
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#include "util_boundbox.h"
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#include "util_types.h"
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CCL_NAMESPACE_BEGIN
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/* SSE replacements */
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__forceinline void prefetch_L1 (const void* /*ptr*/) { }
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__forceinline void prefetch_L2 (const void* /*ptr*/) { }
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__forceinline void prefetch_L3 (const void* /*ptr*/) { }
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__forceinline void prefetch_NTA(const void* /*ptr*/) { }
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template<size_t src> __forceinline float extract(const int4& b)
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{ return b[src]; }
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template<size_t dst> __forceinline const float4 insert(const float4& a, const float b)
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{ float4 r = a; r[dst] = b; return r; }
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__forceinline int get_best_dimension(const float4& bestSAH)
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{
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// return (int)__bsf(movemask(reduce_min(bestSAH) == bestSAH));
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float minSAH = min(bestSAH.x, min(bestSAH.y, bestSAH.z));
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if(bestSAH.x == minSAH) return 0;
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else if(bestSAH.y == minSAH) return 1;
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else return 2;
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}
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/* BVH Object Binning */
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BVHObjectBinning::BVHObjectBinning(const BVHRange& job,
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BVHReference *prims,
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const BVHUnaligned *unaligned_heuristic,
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const Transform *aligned_space)
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: BVHRange(job),
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splitSAH(FLT_MAX),
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dim(0),
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pos(0),
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unaligned_heuristic_(unaligned_heuristic),
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aligned_space_(aligned_space)
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{
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if(aligned_space_ == NULL) {
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bounds_ = bounds();
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cent_bounds_ = cent_bounds();
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}
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else {
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/* TODO(sergey): With some additional storage we can avoid
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* need in re-calculating this.
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*/
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bounds_ = unaligned_heuristic->compute_aligned_boundbox(
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*this,
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prims,
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*aligned_space,
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¢_bounds_);
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}
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/* compute number of bins to use and precompute scaling factor for binning */
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num_bins = min(size_t(MAX_BINS), size_t(4.0f + 0.05f*size()));
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scale = rcp(cent_bounds_.size()) * make_float3((float)num_bins);
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/* initialize binning counter and bounds */
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BoundBox bin_bounds[MAX_BINS][4]; /* bounds for every bin in every dimension */
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int4 bin_count[MAX_BINS]; /* number of primitives mapped to bin */
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for(size_t i = 0; i < num_bins; i++) {
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bin_count[i] = make_int4(0);
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bin_bounds[i][0] = bin_bounds[i][1] = bin_bounds[i][2] = BoundBox::empty;
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}
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/* map geometry to bins, unrolled once */
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{
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ssize_t i;
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for(i = 0; i < ssize_t(size()) - 1; i += 2) {
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prefetch_L2(&prims[start() + i + 8]);
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/* map even and odd primitive to bin */
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const BVHReference& prim0 = prims[start() + i + 0];
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const BVHReference& prim1 = prims[start() + i + 1];
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BoundBox bounds0 = get_prim_bounds(prim0);
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BoundBox bounds1 = get_prim_bounds(prim1);
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int4 bin0 = get_bin(bounds0);
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int4 bin1 = get_bin(bounds1);
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/* increase bounds for bins for even primitive */
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int b00 = (int)extract<0>(bin0); bin_count[b00][0]++; bin_bounds[b00][0].grow(bounds0);
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int b01 = (int)extract<1>(bin0); bin_count[b01][1]++; bin_bounds[b01][1].grow(bounds0);
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int b02 = (int)extract<2>(bin0); bin_count[b02][2]++; bin_bounds[b02][2].grow(bounds0);
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/* increase bounds of bins for odd primitive */
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int b10 = (int)extract<0>(bin1); bin_count[b10][0]++; bin_bounds[b10][0].grow(bounds1);
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int b11 = (int)extract<1>(bin1); bin_count[b11][1]++; bin_bounds[b11][1].grow(bounds1);
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int b12 = (int)extract<2>(bin1); bin_count[b12][2]++; bin_bounds[b12][2].grow(bounds1);
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}
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/* for uneven number of primitives */
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if(i < ssize_t(size())) {
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/* map primitive to bin */
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const BVHReference& prim0 = prims[start() + i];
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BoundBox bounds0 = get_prim_bounds(prim0);
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int4 bin0 = get_bin(bounds0);
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/* increase bounds of bins */
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int b00 = (int)extract<0>(bin0); bin_count[b00][0]++; bin_bounds[b00][0].grow(bounds0);
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int b01 = (int)extract<1>(bin0); bin_count[b01][1]++; bin_bounds[b01][1].grow(bounds0);
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int b02 = (int)extract<2>(bin0); bin_count[b02][2]++; bin_bounds[b02][2].grow(bounds0);
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}
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}
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/* sweep from right to left and compute parallel prefix of merged bounds */
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float4 r_area[MAX_BINS]; /* area of bounds of primitives on the right */
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float4 r_count[MAX_BINS]; /* number of primitives on the right */
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int4 count = make_int4(0);
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BoundBox bx = BoundBox::empty;
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BoundBox by = BoundBox::empty;
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BoundBox bz = BoundBox::empty;
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for(size_t i = num_bins - 1; i > 0; i--) {
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count = count + bin_count[i];
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r_count[i] = blocks(count);
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bx = merge(bx,bin_bounds[i][0]); r_area[i][0] = bx.half_area();
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by = merge(by,bin_bounds[i][1]); r_area[i][1] = by.half_area();
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bz = merge(bz,bin_bounds[i][2]); r_area[i][2] = bz.half_area();
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r_area[i][3] = r_area[i][2];
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}
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/* sweep from left to right and compute SAH */
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int4 ii = make_int4(1);
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float4 bestSAH = make_float4(FLT_MAX);
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int4 bestSplit = make_int4(-1);
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count = make_int4(0);
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bx = BoundBox::empty;
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by = BoundBox::empty;
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bz = BoundBox::empty;
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for(size_t i = 1; i < num_bins; i++, ii += make_int4(1)) {
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count = count + bin_count[i-1];
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bx = merge(bx,bin_bounds[i-1][0]); float Ax = bx.half_area();
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by = merge(by,bin_bounds[i-1][1]); float Ay = by.half_area();
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bz = merge(bz,bin_bounds[i-1][2]); float Az = bz.half_area();
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float4 lCount = blocks(count);
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float4 lArea = make_float4(Ax,Ay,Az,Az);
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float4 sah = lArea*lCount + r_area[i]*r_count[i];
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bestSplit = select(sah < bestSAH,ii,bestSplit);
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bestSAH = min(sah,bestSAH);
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}
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int4 mask = float3_to_float4(cent_bounds_.size()) <= make_float4(0.0f);
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bestSAH = insert<3>(select(mask, make_float4(FLT_MAX), bestSAH), FLT_MAX);
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/* find best dimension */
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dim = get_best_dimension(bestSAH);
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splitSAH = bestSAH[dim];
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pos = bestSplit[dim];
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leafSAH = bounds_.half_area() * blocks(size());
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}
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void BVHObjectBinning::split(BVHReference* prims,
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BVHObjectBinning& left_o,
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BVHObjectBinning& right_o) const
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{
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size_t N = size();
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BoundBox lgeom_bounds = BoundBox::empty;
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BoundBox rgeom_bounds = BoundBox::empty;
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BoundBox lcent_bounds = BoundBox::empty;
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BoundBox rcent_bounds = BoundBox::empty;
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ssize_t l = 0, r = N-1;
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while(l <= r) {
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prefetch_L2(&prims[start() + l + 8]);
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prefetch_L2(&prims[start() + r - 8]);
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BVHReference prim = prims[start() + l];
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BoundBox unaligned_bounds = get_prim_bounds(prim);
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float3 unaligned_center = unaligned_bounds.center2();
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float3 center = prim.bounds().center2();
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if(get_bin(unaligned_center)[dim] < pos) {
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lgeom_bounds.grow(prim.bounds());
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lcent_bounds.grow(center);
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l++;
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}
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else {
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rgeom_bounds.grow(prim.bounds());
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rcent_bounds.grow(center);
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swap(prims[start()+l],prims[start()+r]);
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r--;
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}
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}
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/* finish */
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if(l != 0 && N-1-r != 0) {
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right_o = BVHObjectBinning(BVHRange(rgeom_bounds, rcent_bounds, start() + l, N-1-r), prims);
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left_o = BVHObjectBinning(BVHRange(lgeom_bounds, lcent_bounds, start(), l), prims);
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return;
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}
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/* object medium split if we did not make progress, can happen when all
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* primitives have same centroid */
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lgeom_bounds = BoundBox::empty;
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rgeom_bounds = BoundBox::empty;
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lcent_bounds = BoundBox::empty;
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rcent_bounds = BoundBox::empty;
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for(size_t i = 0; i < N/2; i++) {
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lgeom_bounds.grow(prims[start()+i].bounds());
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lcent_bounds.grow(prims[start()+i].bounds().center2());
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}
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for(size_t i = N/2; i < N; i++) {
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rgeom_bounds.grow(prims[start()+i].bounds());
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rcent_bounds.grow(prims[start()+i].bounds().center2());
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}
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right_o = BVHObjectBinning(BVHRange(rgeom_bounds, rcent_bounds, start() + N/2, N/2 + N%2), prims);
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left_o = BVHObjectBinning(BVHRange(lgeom_bounds, lcent_bounds, start(), N/2), prims);
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}
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CCL_NAMESPACE_END
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