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blender/intern/cycles/kernel/bvh/bvh_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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/*
* Adapted from code Copyright 2009-2010 NVIDIA Corporation,
* and code copyright 2009-2012 Intel Corporation
*
* Modifications 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.
*/
#ifdef __QBVH__
# include "qbvh_traversal.h"
#endif
#if BVH_FEATURE(BVH_HAIR)
# define NODE_INTERSECT bvh_node_intersect
# define NODE_INTERSECT_ROBUST bvh_node_intersect_robust
#else
# define NODE_INTERSECT bvh_aligned_node_intersect
# define NODE_INTERSECT_ROBUST bvh_aligned_node_intersect_robust
#endif
/* 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
*
*/
ccl_device_noinline bool BVH_FUNCTION_FULL_NAME(BVH)(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:
* - 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 */
int traversal_stack[BVH_STACK_SIZE];
traversal_stack[0] = ENTRYPOINT_SENTINEL;
/* traversal variables in registers */
int stack_ptr = 0;
int node_addr = kernel_data.bvh.root;
/* 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
isect->t = ray->t;
isect->u = 0.0f;
isect->v = 0.0f;
isect->prim = PRIM_NONE;
isect->object = OBJECT_NONE;
BVH_DEBUG_INIT();
#if defined(__KERNEL_SSE2__)
const shuffle_swap_t shuf_identity = shuffle_swap_identity();
const shuffle_swap_t shuf_swap = shuffle_swap_swap();
const ssef pn = cast(ssei(0, 0, 0x80000000, 0x80000000));
ssef Psplat[3], idirsplat[3];
# if BVH_FEATURE(BVH_HAIR)
ssef tnear(0.0f), tfar(isect->t);
# endif
shuffle_swap_t shufflexyz[3];
Psplat[0] = ssef(P.x);
Psplat[1] = ssef(P.y);
Psplat[2] = ssef(P.z);
ssef tsplat(0.0f, 0.0f, -isect->t, -isect->t);
gen_idirsplat_swap(pn, shuf_identity, shuf_swap, idir, idirsplat, shufflexyz);
#endif
/* traversal loop */
do {
do {
/* traverse internal nodes */
while(node_addr >= 0 && node_addr != ENTRYPOINT_SENTINEL) {
int node_addr_child1, traverse_mask;
float dist[2];
float4 cnodes = kernel_tex_fetch(__bvh_nodes, node_addr+0);
#if !defined(__KERNEL_SSE2__)
# if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
if(difl != 0.0f) {
traverse_mask = NODE_INTERSECT_ROBUST(kg,
P,
# if BVH_FEATURE(BVH_HAIR)
dir,
# endif
idir,
isect->t,
difl,
extmax,
node_addr,
visibility,
dist);
}
else
# endif
{
traverse_mask = NODE_INTERSECT(kg,
P,
# if BVH_FEATURE(BVH_HAIR)
dir,
# endif
idir,
isect->t,
node_addr,
visibility,
dist);
}
#else // __KERNEL_SSE2__
# if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
if(difl != 0.0f) {
traverse_mask = NODE_INTERSECT_ROBUST(kg,
P,
dir,
# if BVH_FEATURE(BVH_HAIR)
tnear,
tfar,
# endif
tsplat,
Psplat,
idirsplat,
shufflexyz,
difl,
extmax,
node_addr,
visibility,
dist);
}
else
# endif
{
traverse_mask = NODE_INTERSECT(kg,
P,
dir,
# if BVH_FEATURE(BVH_HAIR)
tnear,
tfar,
# endif
tsplat,
Psplat,
idirsplat,
shufflexyz,
node_addr,
visibility,
dist);
}
#endif // __KERNEL_SSE2__
node_addr = __float_as_int(cnodes.z);
node_addr_child1 = __float_as_int(cnodes.w);
if(traverse_mask == 3) {
/* Both children were intersected, push the farther one. */
bool is_closest_child1 = (dist[1] < dist[0]);
if(is_closest_child1) {
int tmp = node_addr;
node_addr = node_addr_child1;
node_addr_child1 = tmp;
}
++stack_ptr;
kernel_assert(stack_ptr < BVH_STACK_SIZE);
traversal_stack[stack_ptr] = node_addr_child1;
}
else {
/* One child was intersected. */
if(traverse_mask == 2) {
node_addr = node_addr_child1;
}
else if(traverse_mask == 0) {
/* Neither child was intersected. */
node_addr = traversal_stack[stack_ptr];
--stack_ptr;
}
}
BVH_DEBUG_NEXT_NODE();
}
/* if node is leaf, fetch triangle list */
if(node_addr < 0) {
float4 leaf = kernel_tex_fetch(__bvh_leaf_nodes, (-node_addr-1));
int prim_addr = __float_as_int(leaf.x);
#if BVH_FEATURE(BVH_INSTANCING)
if(prim_addr >= 0) {
#endif
const int prim_addr2 = __float_as_int(leaf.y);
const uint type = __float_as_int(leaf.w);
/* pop */
node_addr = traversal_stack[stack_ptr];
--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))
{
/* shadow ray early termination */
#if defined(__KERNEL_SSE2__)
if(visibility == PATH_RAY_SHADOW_OPAQUE)
return true;
tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
# if BVH_FEATURE(BVH_HAIR)
tfar = ssef(isect->t);
# endif
#else
if(visibility == PATH_RAY_SHADOW_OPAQUE)
return true;
#endif
}
}
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))
{
/* shadow ray early termination */
# if defined(__KERNEL_SSE2__)
if(visibility == PATH_RAY_SHADOW_OPAQUE)
return true;
tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
# if BVH_FEATURE(BVH_HAIR)
tfar = ssef(isect->t);
# endif
# else
if(visibility == PATH_RAY_SHADOW_OPAQUE)
return true;
# endif
}
}
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) {
/* shadow ray early termination */
# if defined(__KERNEL_SSE2__)
if(visibility == PATH_RAY_SHADOW_OPAQUE)
return true;
tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
# if BVH_FEATURE(BVH_HAIR)
tfar = ssef(isect->t);
# endif
# else
if(visibility == PATH_RAY_SHADOW_OPAQUE)
return true;
# endif
}
}
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)
isect->t = bvh_instance_motion_push(kg, object, ray, &P, &dir, &idir, isect->t, &ob_itfm);
# else
isect->t = bvh_instance_push(kg, object, ray, &P, &dir, &idir, isect->t);
# endif
# if defined(__KERNEL_SSE2__)
Psplat[0] = ssef(P.x);
Psplat[1] = ssef(P.y);
Psplat[2] = ssef(P.z);
tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
# if BVH_FEATURE(BVH_HAIR)
tfar = ssef(isect->t);
# endif
gen_idirsplat_swap(pn, shuf_identity, shuf_swap, idir, idirsplat, shufflexyz);
# endif
++stack_ptr;
kernel_assert(stack_ptr < BVH_STACK_SIZE);
traversal_stack[stack_ptr] = ENTRYPOINT_SENTINEL;
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
# if defined(__KERNEL_SSE2__)
Psplat[0] = ssef(P.x);
Psplat[1] = ssef(P.y);
Psplat[2] = ssef(P.z);
tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
# if BVH_FEATURE(BVH_HAIR)
tfar = ssef(isect->t);
# endif
gen_idirsplat_swap(pn, shuf_identity, shuf_swap, idir, idirsplat, shufflexyz);
# endif
object = OBJECT_NONE;
node_addr = traversal_stack[stack_ptr];
--stack_ptr;
}
#endif /* FEATURE(BVH_INSTANCING) */
} while(node_addr != ENTRYPOINT_SENTINEL);
return (isect->prim != PRIM_NONE);
}
ccl_device_inline bool BVH_FUNCTION_NAME(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
)
{
#ifdef __QBVH__
if(kernel_data.bvh.use_qbvh) {
return BVH_FUNCTION_FULL_NAME(QBVH)(kg,
ray,
isect,
visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
, lcg_state,
difl,
extmax
#endif
);
}
else
#endif
{
kernel_assert(kernel_data.bvh.use_qbvh == false);
return BVH_FUNCTION_FULL_NAME(BVH)(kg,
ray,
isect,
visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
, lcg_state,
difl,
extmax
#endif
);
}
}
#undef BVH_FUNCTION_NAME
#undef BVH_FUNCTION_FEATURES
#undef NODE_INTERSECT
#undef NODE_INTERSECT_ROBUST
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