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blender/intern/cycles/kernel/bvh/qbvh_traversal.h
Sergey Sharybin 6ea54fe9ff Cycles: Switch to reformulated Pluecker ray/triangle intersection 
The intention of this commit it to address issues mentioned in the
reports T43865,T50164 and T50452.

The code is based on Embree code with some extra vectorization
to speed up single ray to single triangle intersection.

Unfortunately, such a fix is not coming for free. There is some
slowdown for AVX2 processors, mainly due to different vectorization
code, which caused different number of instructions to be executed
and different instructions-per-cycle counters. But on another hand
this commit makes pre-AVX2 platforms such as AVX and SSE4.1 a bit
faster. The prerformance goes as following:

              2.78c AVX2   2.78c AVX   Patch AVX2         Patch AVX
BMW            05:21.09     06:05.34    05:32.97 (+3.5%)   05:34.97 (-8.5%)
Classroom      16:55.36     18:24.51    17:10.41 (+1.4%)   17:15.87 (-6.3%)
Fishy Cat      08:08.49     08:36.26    08:09.19 (+0.2%)   08:12.25 (-4.7%
Koro           11:22.54     11:45.24    11:13.25 (-1.5%)   11:43.81 (-0.3%)
Barcelone      14:18.32     16:09.46    14:15.20 (-0.4%)   14:25.15 (-10.8%)

On GPU the performance is about 1.5-2% slower in my tests on GTX1080
but afraid we can't do much as a part of this chaneg here and
consider it a price to pay for more proper intersection check.

Made in collaboration with Maxym Dmytrychenko, big thanks to him!

Reviewers: brecht, juicyfruit, lukasstockner97, dingto

Differential Revision: https://developer.blender.org/D1574
2017-03-28 17:26:47 +02:00

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/*
* Copyright 2011-2013 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.
*/
/* This is a template BVH traversal function, where various features can be
* enabled/disabled. This way we can compile optimized versions for each case
* without new features slowing things down.
*
* BVH_INSTANCING: object instancing
* BVH_HAIR: hair curve rendering
* BVH_HAIR_MINIMUM_WIDTH: hair curve rendering with minimum width
* BVH_MOTION: motion blur rendering
*
*/
#if BVH_FEATURE(BVH_HAIR)
# define NODE_INTERSECT qbvh_node_intersect
# define NODE_INTERSECT_ROBUST qbvh_node_intersect_robust
#else
# define NODE_INTERSECT qbvh_aligned_node_intersect
# define NODE_INTERSECT_ROBUST qbvh_aligned_node_intersect_robust
#endif
ccl_device bool BVH_FUNCTION_FULL_NAME(QBVH)(KernelGlobals *kg,
const Ray *ray,
Intersection *isect,
const uint visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
,uint *lcg_state,
float difl,
float extmax
#endif
)
{
/* TODO(sergey):
* - Test if pushing distance on the stack helps (for non shadow rays).
* - Separate version for shadow rays.
* - Likely and unlikely for if() statements.
* - Test restrict attribute for pointers.
*/
/* Traversal stack in CUDA thread-local memory. */
QBVHStackItem traversal_stack[BVH_QSTACK_SIZE];
traversal_stack[0].addr = ENTRYPOINT_SENTINEL;
traversal_stack[0].dist = -FLT_MAX;
/* Traversal variables in registers. */
int stack_ptr = 0;
int node_addr = kernel_data.bvh.root;
float node_dist = -FLT_MAX;
/* Ray parameters in registers. */
float3 P = ray->P;
float3 dir = bvh_clamp_direction(ray->D);
float3 idir = bvh_inverse_direction(dir);
int object = OBJECT_NONE;
#if BVH_FEATURE(BVH_MOTION)
Transform ob_itfm;
#endif
#ifndef __KERNEL_SSE41__
if(!isfinite(P.x)) {
return false;
}
#endif
isect->t = ray->t;
isect->u = 0.0f;
isect->v = 0.0f;
isect->prim = PRIM_NONE;
isect->object = OBJECT_NONE;
BVH_DEBUG_INIT();
ssef tnear(0.0f), tfar(ray->t);
#if BVH_FEATURE(BVH_HAIR)
sse3f dir4(ssef(dir.x), ssef(dir.y), ssef(dir.z));
#endif
sse3f idir4(ssef(idir.x), ssef(idir.y), ssef(idir.z));
#ifdef __KERNEL_AVX2__
float3 P_idir = P*idir;
sse3f P_idir4 = sse3f(P_idir.x, P_idir.y, P_idir.z);
#endif
#if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
sse3f org4 = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
#endif
/* Offsets to select the side that becomes the lower or upper bound. */
int near_x, near_y, near_z;
int far_x, far_y, far_z;
qbvh_near_far_idx_calc(idir,
&near_x, &near_y, &near_z,
&far_x, &far_y, &far_z);
/* Traversal loop. */
do {
do {
/* Traverse internal nodes. */
while(node_addr >= 0 && node_addr != ENTRYPOINT_SENTINEL) {
float4 inodes = kernel_tex_fetch(__bvh_nodes, node_addr+0);
if(UNLIKELY(node_dist > isect->t)
#if BVH_FEATURE(BVH_MOTION)
|| UNLIKELY(ray->time < inodes.y)
|| UNLIKELY(ray->time > inodes.z)
#endif
#ifdef __VISIBILITY_FLAG__
|| (__float_as_uint(inodes.x) & visibility) == 0)
#endif
{
/* Pop. */
node_addr = traversal_stack[stack_ptr].addr;
node_dist = traversal_stack[stack_ptr].dist;
--stack_ptr;
continue;
}
int child_mask;
ssef dist;
BVH_DEBUG_NEXT_NODE();
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
if(difl != 0.0f) {
/* NOTE: We extend all the child BB instead of fetching
* and checking visibility flags for each of the,
*
* Need to test if doing opposite would be any faster.
*/
child_mask = NODE_INTERSECT_ROBUST(kg,
tnear,
tfar,
# ifdef __KERNEL_AVX2__
P_idir4,
# endif
# if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
org4,
# endif
# if BVH_FEATURE(BVH_HAIR)
dir4,
# endif
idir4,
near_x, near_y, near_z,
far_x, far_y, far_z,
node_addr,
difl,
&dist);
}
else
#endif /* BVH_HAIR_MINIMUM_WIDTH */
{
child_mask = NODE_INTERSECT(kg,
tnear,
tfar,
#ifdef __KERNEL_AVX2__
P_idir4,
#endif
#if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
org4,
#endif
#if BVH_FEATURE(BVH_HAIR)
dir4,
#endif
idir4,
near_x, near_y, near_z,
far_x, far_y, far_z,
node_addr,
&dist);
}
if(child_mask != 0) {
float4 cnodes;
/* TODO(sergey): Investigate whether moving cnodes upwards
* gives a speedup (will be different cache pattern but will
* avoid extra check here),
*/
#if BVH_FEATURE(BVH_HAIR)
if(__float_as_uint(inodes.x) & PATH_RAY_NODE_UNALIGNED) {
cnodes = kernel_tex_fetch(__bvh_nodes, node_addr+13);
}
else
#endif
{
cnodes = kernel_tex_fetch(__bvh_nodes, node_addr+7);
}
/* One child is hit, continue with that child. */
int r = __bscf(child_mask);
float d0 = ((float*)&dist)[r];
if(child_mask == 0) {
node_addr = __float_as_int(cnodes[r]);
node_dist = d0;
continue;
}
/* Two children are hit, push far child, and continue with
* closer child.
*/
int c0 = __float_as_int(cnodes[r]);
r = __bscf(child_mask);
int c1 = __float_as_int(cnodes[r]);
float d1 = ((float*)&dist)[r];
if(child_mask == 0) {
if(d1 < d0) {
node_addr = c1;
node_dist = d1;
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c0;
traversal_stack[stack_ptr].dist = d0;
continue;
}
else {
node_addr = c0;
node_dist = d0;
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c1;
traversal_stack[stack_ptr].dist = d1;
continue;
}
}
/* Here starts the slow path for 3 or 4 hit children. We push
* all nodes onto the stack to sort them there.
*/
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c1;
traversal_stack[stack_ptr].dist = d1;
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c0;
traversal_stack[stack_ptr].dist = d0;
/* Three children are hit, push all onto stack and sort 3
* stack items, continue with closest child.
*/
r = __bscf(child_mask);
int c2 = __float_as_int(cnodes[r]);
float d2 = ((float*)&dist)[r];
if(child_mask == 0) {
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c2;
traversal_stack[stack_ptr].dist = d2;
qbvh_stack_sort(&traversal_stack[stack_ptr],
&traversal_stack[stack_ptr - 1],
&traversal_stack[stack_ptr - 2]);
node_addr = traversal_stack[stack_ptr].addr;
node_dist = traversal_stack[stack_ptr].dist;
--stack_ptr;
continue;
}
/* Four children are hit, push all onto stack and sort 4
* stack items, continue with closest child.
*/
r = __bscf(child_mask);
int c3 = __float_as_int(cnodes[r]);
float d3 = ((float*)&dist)[r];
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c3;
traversal_stack[stack_ptr].dist = d3;
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = c2;
traversal_stack[stack_ptr].dist = d2;
qbvh_stack_sort(&traversal_stack[stack_ptr],
&traversal_stack[stack_ptr - 1],
&traversal_stack[stack_ptr - 2],
&traversal_stack[stack_ptr - 3]);
}
node_addr = traversal_stack[stack_ptr].addr;
node_dist = traversal_stack[stack_ptr].dist;
--stack_ptr;
}
/* If node is leaf, fetch triangle list. */
if(node_addr < 0) {
float4 leaf = kernel_tex_fetch(__bvh_leaf_nodes, (-node_addr-1));
#ifdef __VISIBILITY_FLAG__
if(UNLIKELY((node_dist > isect->t) ||
((__float_as_uint(leaf.z) & visibility) == 0)))
#else
if(UNLIKELY((node_dist > isect->t)))
#endif
{
/* Pop. */
node_addr = traversal_stack[stack_ptr].addr;
node_dist = traversal_stack[stack_ptr].dist;
--stack_ptr;
continue;
}
int prim_addr = __float_as_int(leaf.x);
#if BVH_FEATURE(BVH_INSTANCING)
if(prim_addr >= 0) {
#endif
int prim_addr2 = __float_as_int(leaf.y);
const uint type = __float_as_int(leaf.w);
/* Pop. */
node_addr = traversal_stack[stack_ptr].addr;
node_dist = traversal_stack[stack_ptr].dist;
--stack_ptr;
/* Primitive intersection. */
switch(type & PRIMITIVE_ALL) {
case PRIMITIVE_TRIANGLE: {
for(; prim_addr < prim_addr2; prim_addr++) {
BVH_DEBUG_NEXT_INTERSECTION();
kernel_assert(kernel_tex_fetch(__prim_type, prim_addr) == type);
if(triangle_intersect(kg,
isect,
P,
dir,
visibility,
object,
prim_addr)) {
tfar = ssef(isect->t);
/* Shadow ray early termination. */
if(visibility == PATH_RAY_SHADOW_OPAQUE) {
return true;
}
}
}
break;
}
#if BVH_FEATURE(BVH_MOTION)
case PRIMITIVE_MOTION_TRIANGLE: {
for(; prim_addr < prim_addr2; prim_addr++) {
BVH_DEBUG_NEXT_INTERSECTION();
kernel_assert(kernel_tex_fetch(__prim_type, prim_addr) == type);
if(motion_triangle_intersect(kg,
isect,
P,
dir,
ray->time,
visibility,
object,
prim_addr)) {
tfar = ssef(isect->t);
/* Shadow ray early termination. */
if(visibility == PATH_RAY_SHADOW_OPAQUE) {
return true;
}
}
}
break;
}
#endif /* BVH_FEATURE(BVH_MOTION) */
#if BVH_FEATURE(BVH_HAIR)
case PRIMITIVE_CURVE:
case PRIMITIVE_MOTION_CURVE: {
for(; prim_addr < prim_addr2; prim_addr++) {
BVH_DEBUG_NEXT_INTERSECTION();
const uint curve_type = kernel_tex_fetch(__prim_type, prim_addr);
kernel_assert((curve_type & PRIMITIVE_ALL) == (type & PRIMITIVE_ALL));
bool hit;
if(kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE) {
hit = bvh_cardinal_curve_intersect(kg,
isect,
P,
dir,
visibility,
object,
prim_addr,
ray->time,
curve_type,
lcg_state,
difl,
extmax);
}
else {
hit = bvh_curve_intersect(kg,
isect,
P,
dir,
visibility,
object,
prim_addr,
ray->time,
curve_type,
lcg_state,
difl,
extmax);
}
if(hit) {
tfar = ssef(isect->t);
/* Shadow ray early termination. */
if(visibility == PATH_RAY_SHADOW_OPAQUE) {
return true;
}
}
}
break;
}
#endif /* BVH_FEATURE(BVH_HAIR) */
}
}
#if BVH_FEATURE(BVH_INSTANCING)
else {
/* Instance push. */
object = kernel_tex_fetch(__prim_object, -prim_addr-1);
# if BVH_FEATURE(BVH_MOTION)
qbvh_instance_motion_push(kg, object, ray, &P, &dir, &idir, &isect->t, &node_dist, &ob_itfm);
# else
qbvh_instance_push(kg, object, ray, &P, &dir, &idir, &isect->t, &node_dist);
# endif
qbvh_near_far_idx_calc(idir,
&near_x, &near_y, &near_z,
&far_x, &far_y, &far_z);
tfar = ssef(isect->t);
# if BVH_FEATURE(BVH_HAIR)
dir4 = sse3f(ssef(dir.x), ssef(dir.y), ssef(dir.z));
# endif
idir4 = sse3f(ssef(idir.x), ssef(idir.y), ssef(idir.z));
# ifdef __KERNEL_AVX2__
P_idir = P*idir;
P_idir4 = sse3f(P_idir.x, P_idir.y, P_idir.z);
# endif
# if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
org4 = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
# endif
++stack_ptr;
kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
traversal_stack[stack_ptr].addr = ENTRYPOINT_SENTINEL;
traversal_stack[stack_ptr].dist = -FLT_MAX;
node_addr = kernel_tex_fetch(__object_node, object);
BVH_DEBUG_NEXT_INSTANCE();
}
}
#endif /* FEATURE(BVH_INSTANCING) */
} while(node_addr != ENTRYPOINT_SENTINEL);
#if BVH_FEATURE(BVH_INSTANCING)
if(stack_ptr >= 0) {
kernel_assert(object != OBJECT_NONE);
/* Instance pop. */
# if BVH_FEATURE(BVH_MOTION)
isect->t = bvh_instance_motion_pop(kg, object, ray, &P, &dir, &idir, isect->t, &ob_itfm);
# else
isect->t = bvh_instance_pop(kg, object, ray, &P, &dir, &idir, isect->t);
# endif
qbvh_near_far_idx_calc(idir,
&near_x, &near_y, &near_z,
&far_x, &far_y, &far_z);
tfar = ssef(isect->t);
# if BVH_FEATURE(BVH_HAIR)
dir4 = sse3f(ssef(dir.x), ssef(dir.y), ssef(dir.z));
# endif
idir4 = sse3f(ssef(idir.x), ssef(idir.y), ssef(idir.z));
# ifdef __KERNEL_AVX2__
P_idir = P*idir;
P_idir4 = sse3f(P_idir.x, P_idir.y, P_idir.z);
# endif
# if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
org4 = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
# endif
object = OBJECT_NONE;
node_addr = traversal_stack[stack_ptr].addr;
node_dist = traversal_stack[stack_ptr].dist;
--stack_ptr;
}
#endif /* FEATURE(BVH_INSTANCING) */
} while(node_addr != ENTRYPOINT_SENTINEL);
return (isect->prim != PRIM_NONE);
}
#undef NODE_INTERSECT
#undef NODE_INTERSECT_ROBUST
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