size_t BVH4MB::rotate(Base* nodeID, size_t depth) { /*! nothing to rotate if we reached a leaf node. */ if (nodeID->isLeaf()) return 0; Node* parent = nodeID->node(); /*! rotate all children first */ ssei cdepth; for (size_t c=0; c<4; c++) cdepth[c] = (int)rotate(parent->child[c],depth+1); /* compute current area of all children */ ssef sizeX = parent->upper_x-parent->lower_x; ssef sizeY = parent->upper_y-parent->lower_y; ssef sizeZ = parent->upper_z-parent->lower_z; ssef childArea = sizeX*(sizeY + sizeZ) + sizeY*sizeZ; /*! transpose node bounds */ ssef plower0,plower1,plower2,plower3; transpose(parent->lower_x,parent->lower_y,parent->lower_z,ssef(zero),plower0,plower1,plower2,plower3); ssef pupper0,pupper1,pupper2,pupper3; transpose(parent->upper_x,parent->upper_y,parent->upper_z,ssef(zero),pupper0,pupper1,pupper2,pupper3); BBox<ssef> other0(plower0,pupper0), other1(plower1,pupper1), other2(plower2,pupper2), other3(plower3,pupper3); /*! Find best rotation. We pick a target child of a first child, and swap this with an other child. We perform the best such swap. */ float bestCost = pos_inf; int bestChild = -1, bestTarget = -1, bestOther = -1; for (size_t c=0; c<4; c++) { /*! ignore leaf nodes as we cannot descent into */ if (parent->child[c]->isLeaf()) continue; Node* child = parent->child[c]->node(); /*! transpose child bounds */ ssef clower0,clower1,clower2,clower3; transpose(child->lower_x,child->lower_y,child->lower_z,ssef(zero),clower0,clower1,clower2,clower3); ssef cupper0,cupper1,cupper2,cupper3; transpose(child->upper_x,child->upper_y,child->upper_z,ssef(zero),cupper0,cupper1,cupper2,cupper3); BBox<ssef> target0(clower0,cupper0), target1(clower1,cupper1), target2(clower2,cupper2), target3(clower3,cupper3); /*! put other0 at each target position */ float cost00 = halfArea3f(merge(other0 ,target1,target2,target3)); float cost01 = halfArea3f(merge(target0,other0 ,target2,target3)); float cost02 = halfArea3f(merge(target0,target1,other0 ,target3)); float cost03 = halfArea3f(merge(target0,target1,target2,other0 )); ssef cost0 = ssef(cost00,cost01,cost02,cost03); ssef min0 = vreduce_min(cost0); int pos0 = (int)__bsf(movemask(min0 == cost0)); /*! put other1 at each target position */ float cost10 = halfArea3f(merge(other1 ,target1,target2,target3)); float cost11 = halfArea3f(merge(target0,other1 ,target2,target3)); float cost12 = halfArea3f(merge(target0,target1,other1 ,target3)); float cost13 = halfArea3f(merge(target0,target1,target2,other1 )); ssef cost1 = ssef(cost10,cost11,cost12,cost13); ssef min1 = vreduce_min(cost1); int pos1 = (int)__bsf(movemask(min1 == cost1)); /*! put other2 at each target position */ float cost20 = halfArea3f(merge(other2 ,target1,target2,target3)); float cost21 = halfArea3f(merge(target0,other2 ,target2,target3)); float cost22 = halfArea3f(merge(target0,target1,other2 ,target3)); float cost23 = halfArea3f(merge(target0,target1,target2,other2 )); ssef cost2 = ssef(cost20,cost21,cost22,cost23); ssef min2 = vreduce_min(cost2); int pos2 = (int)__bsf(movemask(min2 == cost2)); /*! put other3 at each target position */ float cost30 = halfArea3f(merge(other3 ,target1,target2,target3)); float cost31 = halfArea3f(merge(target0,other3 ,target2,target3)); float cost32 = halfArea3f(merge(target0,target1,other3 ,target3)); float cost33 = halfArea3f(merge(target0,target1,target2,other3 )); ssef cost3 = ssef(cost30,cost31,cost32,cost33); ssef min3 = vreduce_min(cost3); int pos3 = (int)__bsf(movemask(min3 == cost3)); /*! find best other child */ ssef otherCost = ssef(extract<0>(min0),extract<0>(min1),extract<0>(min2),extract<0>(min3)); int pos[4] = { pos0,pos1,pos2,pos3 }; sseb valid = ssei(int(depth+1))+cdepth <= ssei(maxDepth); // only select swaps that fulfill depth constraints if (none(valid)) continue; size_t n = select_min(valid,otherCost); float cost = otherCost[n]-childArea[c]; //< increasing the original child bound is bad, decreasing good /*! accept a swap when it reduces cost and is not swapping a node with itself */ if (cost < bestCost && n != c) { bestCost = cost; bestChild = (int)c; bestOther = (int)n; bestTarget = pos[n]; } } /*! if we did not find a swap that improves the SAH then do nothing */ if (bestCost >= 0) return 1+reduce_max(cdepth); /*! perform the best found tree rotation */ Node* child = parent->child[bestChild]->node(); swap(parent,bestOther,child,bestTarget); parent->lower_x[bestChild] = reduce_min(child->lower_x); parent->lower_y[bestChild] = reduce_min(child->lower_y); parent->lower_z[bestChild] = reduce_min(child->lower_z); parent->upper_x[bestChild] = reduce_max(child->upper_x); parent->upper_y[bestChild] = reduce_max(child->upper_y); parent->upper_z[bestChild] = reduce_max(child->upper_z); parent->lower_dx[bestChild] = reduce_min(child->lower_dx); parent->lower_dy[bestChild] = reduce_min(child->lower_dy); parent->lower_dz[bestChild] = reduce_min(child->lower_dz); parent->upper_dx[bestChild] = reduce_max(child->upper_dx); parent->upper_dy[bestChild] = reduce_max(child->upper_dy); parent->upper_dz[bestChild] = reduce_max(child->upper_dz); /*! This returned depth is conservative as the child that was * pulled up in the tree could have been on the critical path. */ cdepth[bestOther]++; // bestOther was pushed down one level return 1+reduce_max(cdepth); }
size_t BVHNRotate<4>::rotate(NodeRef parentRef, size_t depth) { /*! nothing to rotate if we reached a leaf node. */ if (parentRef.isBarrier()) return 0; if (parentRef.isLeaf()) return 0; Node* parent = parentRef.node(); /*! rotate all children first */ vint4 cdepth; for (size_t c=0; c<4; c++) cdepth[c] = (int)rotate(parent->child(c),depth+1); /* compute current areas of all children */ vfloat4 sizeX = parent->upper_x-parent->lower_x; vfloat4 sizeY = parent->upper_y-parent->lower_y; vfloat4 sizeZ = parent->upper_z-parent->lower_z; vfloat4 childArea = sizeX*(sizeY + sizeZ) + sizeY*sizeZ; /*! get node bounds */ BBox<vfloat4> child1_0,child1_1,child1_2,child1_3; parent->bounds(child1_0,child1_1,child1_2,child1_3); /*! Find best rotation. We pick a first child (child1) and a sub-child (child2child) of a different second child (child2), and swap child1 and child2child. We perform the best such swap. */ float bestArea = 0; size_t bestChild1 = -1, bestChild2 = -1, bestChild2Child = -1; for (size_t c2=0; c2<4; c2++) { /*! ignore leaf nodes as we cannot descent into them */ if (parent->child(c2).isBarrier()) continue; if (parent->child(c2).isLeaf()) continue; Node* child2 = parent->child(c2).node(); /*! transpose child bounds */ BBox<vfloat4> child2c0,child2c1,child2c2,child2c3; child2->bounds(child2c0,child2c1,child2c2,child2c3); /*! put child1_0 at each child2 position */ float cost00 = halfArea3f(merge(child1_0,child2c1,child2c2,child2c3)); float cost01 = halfArea3f(merge(child2c0,child1_0,child2c2,child2c3)); float cost02 = halfArea3f(merge(child2c0,child2c1,child1_0,child2c3)); float cost03 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_0)); vfloat4 cost0 = vfloat4(cost00,cost01,cost02,cost03); vfloat4 min0 = vreduce_min(cost0); int pos0 = (int)__bsf(movemask(min0 == cost0)); /*! put child1_1 at each child2 position */ float cost10 = halfArea3f(merge(child1_1,child2c1,child2c2,child2c3)); float cost11 = halfArea3f(merge(child2c0,child1_1,child2c2,child2c3)); float cost12 = halfArea3f(merge(child2c0,child2c1,child1_1,child2c3)); float cost13 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_1)); vfloat4 cost1 = vfloat4(cost10,cost11,cost12,cost13); vfloat4 min1 = vreduce_min(cost1); int pos1 = (int)__bsf(movemask(min1 == cost1)); /*! put child1_2 at each child2 position */ float cost20 = halfArea3f(merge(child1_2,child2c1,child2c2,child2c3)); float cost21 = halfArea3f(merge(child2c0,child1_2,child2c2,child2c3)); float cost22 = halfArea3f(merge(child2c0,child2c1,child1_2,child2c3)); float cost23 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_2)); vfloat4 cost2 = vfloat4(cost20,cost21,cost22,cost23); vfloat4 min2 = vreduce_min(cost2); int pos2 = (int)__bsf(movemask(min2 == cost2)); /*! put child1_3 at each child2 position */ float cost30 = halfArea3f(merge(child1_3,child2c1,child2c2,child2c3)); float cost31 = halfArea3f(merge(child2c0,child1_3,child2c2,child2c3)); float cost32 = halfArea3f(merge(child2c0,child2c1,child1_3,child2c3)); float cost33 = halfArea3f(merge(child2c0,child2c1,child2c2,child1_3)); vfloat4 cost3 = vfloat4(cost30,cost31,cost32,cost33); vfloat4 min3 = vreduce_min(cost3); int pos3 = (int)__bsf(movemask(min3 == cost3)); /*! find best other child */ vfloat4 area0123 = vfloat4(extract<0>(min0),extract<0>(min1),extract<0>(min2),extract<0>(min3)) - vfloat4(childArea[c2]); int pos[4] = { pos0,pos1,pos2,pos3 }; const size_t mbd = BVH4::maxBuildDepth; vbool4 valid = vint4(int(depth+1))+cdepth <= vint4(mbd); // only select swaps that fulfill depth constraints valid &= vint4(c2) != vint4(step); if (none(valid)) continue; size_t c1 = select_min(valid,area0123); float area = area0123[c1]; if (c1 == c2) continue; // can happen if bounds are NANs /*! accept a swap when it reduces cost and is not swapping a node with itself */ if (area < bestArea) { bestArea = area; bestChild1 = c1; bestChild2 = c2; bestChild2Child = pos[c1]; } } /*! if we did not find a swap that improves the SAH then do nothing */ if (bestChild1 == size_t(-1)) return 1+reduce_max(cdepth); /*! perform the best found tree rotation */ Node* child2 = parent->child(bestChild2).node(); BVH4::swap(parent,bestChild1,child2,bestChild2Child); parent->set(bestChild2,child2->bounds()); BVH4::compact(parent); BVH4::compact(child2); /*! This returned depth is conservative as the child that was * pulled up in the tree could have been on the critical path. */ cdepth[bestChild1]++; // bestChild1 was pushed down one level return 1+reduce_max(cdepth); }