128 lines
5.2 KiB
C++
128 lines
5.2 KiB
C++
// Copyright 2009-2021 Intel Corporation
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// SPDX-License-Identifier: Apache-2.0
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#include "bvh_rotate.h"
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namespace embree
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{
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namespace isa
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{
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/*! Computes half surface area of box. */
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__forceinline float halfArea3f(const BBox<vfloat4>& box) {
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const vfloat4 d = box.size();
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const vfloat4 a = d*shuffle<1,2,0,3>(d);
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return a[0]+a[1]+a[2];
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}
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size_t BVHNRotate<4>::rotate(NodeRef parentRef, size_t depth)
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{
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/*! nothing to rotate if we reached a leaf node. */
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if (parentRef.isBarrier()) return 0;
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if (parentRef.isLeaf()) return 0;
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AABBNode* parent = parentRef.getAABBNode();
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/*! rotate all children first */
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vint4 cdepth;
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for (size_t c=0; c<4; c++)
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cdepth[c] = (int)rotate(parent->child(c),depth+1);
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/* compute current areas of all children */
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vfloat4 sizeX = parent->upper_x-parent->lower_x;
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vfloat4 sizeY = parent->upper_y-parent->lower_y;
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vfloat4 sizeZ = parent->upper_z-parent->lower_z;
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vfloat4 childArea = madd(sizeX,(sizeY + sizeZ),sizeY*sizeZ);
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/*! get node bounds */
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BBox<vfloat4> child1_0,child1_1,child1_2,child1_3;
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parent->bounds(child1_0,child1_1,child1_2,child1_3);
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/*! Find best rotation. We pick a first child (child1) and a sub-child
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(child2child) of a different second child (child2), and swap child1
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and child2child. We perform the best such swap. */
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float bestArea = 0;
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size_t bestChild1 = -1, bestChild2 = -1, bestChild2Child = -1;
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for (size_t c2=0; c2<4; c2++)
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{
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/*! ignore leaf nodes as we cannot descent into them */
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if (parent->child(c2).isBarrier()) continue;
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if (parent->child(c2).isLeaf()) continue;
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AABBNode* child2 = parent->child(c2).getAABBNode();
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/*! transpose child bounds */
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BBox<vfloat4> child2c0,child2c1,child2c2,child2c3;
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child2->bounds(child2c0,child2c1,child2c2,child2c3);
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/*! put child1_0 at each child2 position */
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float cost00 = halfArea3f(merge(child1_0,child2c1,child2c2,child2c3));
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float cost01 = halfArea3f(merge(child2c0,child1_0,child2c2,child2c3));
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float cost02 = halfArea3f(merge(child2c0,child2c1,child1_0,child2c3));
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float cost03 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_0));
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vfloat4 cost0 = vfloat4(cost00,cost01,cost02,cost03);
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vfloat4 min0 = vreduce_min(cost0);
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int pos0 = (int)bsf(movemask(min0 == cost0));
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/*! put child1_1 at each child2 position */
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float cost10 = halfArea3f(merge(child1_1,child2c1,child2c2,child2c3));
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float cost11 = halfArea3f(merge(child2c0,child1_1,child2c2,child2c3));
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float cost12 = halfArea3f(merge(child2c0,child2c1,child1_1,child2c3));
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float cost13 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_1));
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vfloat4 cost1 = vfloat4(cost10,cost11,cost12,cost13);
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vfloat4 min1 = vreduce_min(cost1);
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int pos1 = (int)bsf(movemask(min1 == cost1));
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/*! put child1_2 at each child2 position */
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float cost20 = halfArea3f(merge(child1_2,child2c1,child2c2,child2c3));
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float cost21 = halfArea3f(merge(child2c0,child1_2,child2c2,child2c3));
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float cost22 = halfArea3f(merge(child2c0,child2c1,child1_2,child2c3));
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float cost23 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_2));
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vfloat4 cost2 = vfloat4(cost20,cost21,cost22,cost23);
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vfloat4 min2 = vreduce_min(cost2);
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int pos2 = (int)bsf(movemask(min2 == cost2));
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/*! put child1_3 at each child2 position */
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float cost30 = halfArea3f(merge(child1_3,child2c1,child2c2,child2c3));
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float cost31 = halfArea3f(merge(child2c0,child1_3,child2c2,child2c3));
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float cost32 = halfArea3f(merge(child2c0,child2c1,child1_3,child2c3));
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float cost33 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_3));
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vfloat4 cost3 = vfloat4(cost30,cost31,cost32,cost33);
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vfloat4 min3 = vreduce_min(cost3);
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int pos3 = (int)bsf(movemask(min3 == cost3));
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/*! find best other child */
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vfloat4 area0123 = vfloat4(extract<0>(min0),extract<0>(min1),extract<0>(min2),extract<0>(min3)) - vfloat4(childArea[c2]);
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int pos[4] = { pos0,pos1,pos2,pos3 };
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const size_t mbd = BVH4::maxBuildDepth;
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vbool4 valid = vint4(int(depth+1))+cdepth <= vint4(mbd); // only select swaps that fulfill depth constraints
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valid &= vint4(int(c2)) != vint4(step);
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if (none(valid)) continue;
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size_t c1 = select_min(valid,area0123);
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float area = area0123[c1];
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if (c1 == c2) continue; // can happen if bounds are NANs
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/*! accept a swap when it reduces cost and is not swapping a node with itself */
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if (area < bestArea) {
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bestArea = area;
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bestChild1 = c1;
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bestChild2 = c2;
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bestChild2Child = pos[c1];
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}
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}
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/*! if we did not find a swap that improves the SAH then do nothing */
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if (bestChild1 == size_t(-1)) return 1+reduce_max(cdepth);
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/*! perform the best found tree rotation */
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AABBNode* child2 = parent->child(bestChild2).getAABBNode();
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AABBNode::swap(parent,bestChild1,child2,bestChild2Child);
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parent->setBounds(bestChild2,child2->bounds());
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AABBNode::compact(parent);
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AABBNode::compact(child2);
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/*! This returned depth is conservative as the child that was
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* pulled up in the tree could have been on the critical path. */
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cdepth[bestChild1]++; // bestChild1 was pushed down one level
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return 1+reduce_max(cdepth);
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}
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}
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}
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