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blender/intern/cycles/kernel/geom/geom_triangle.h
Sergey Sharybin f770bc4757 Cycles: Implement watertight ray/triangle intersection 
Using this paper: Sven Woop, Watertight Ray/Triangle Intersection

  http://jcgt.org/published/0002/01/05/paper.pdf

This change is expected to address quite reasonable amount of reports from the
bug tracker, plus it might help reducing the noise in some scenes.

Unfortunately, it's currently about 7% slower than the previous solution with
pre-computed triangle plane equations, but maybe with some smart tweaks to the
code (tests reshuffle, using SIMD in a nice way or so) we can avoid the speed
regression.

But perhaps smartest thing to do here would be to change single triangle / ray
intersection with multiple triangles / ray intersections. That's how Embree does
this and it's watertight single ray intersection is not any faster that this.

Currently only triangle intersection is modified accordingly to the paper, in
the future we would also want to modify the node / ray intersection.

Reviewers: brecht, juicyfruit

Subscribers: dingto, ton

Differential Revision: https://developer.blender.org/D819
2014-12-25 02:50:49 +05:00

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/*
* Adapted from code Copyright 2009-2010 NVIDIA Corporation
* Modifications Copyright 2011, 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.
*/
/* Triangle Primitive
*
* Basic triangle with 3 vertices is used to represent mesh surfaces. For BVH
* ray intersection we use a precomputed triangle storage to accelerate
* intersection at the cost of more memory usage */
CCL_NAMESPACE_BEGIN
/* normal on triangle */
ccl_device_inline float3 triangle_normal(KernelGlobals *kg, ShaderData *sd)
{
/* load triangle vertices */
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
float3 v0 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.x)));
float3 v1 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.y)));
float3 v2 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.z)));
/* return normal */
if(sd->flag & SD_NEGATIVE_SCALE_APPLIED)
return normalize(cross(v2 - v0, v1 - v0));
else
return normalize(cross(v1 - v0, v2 - v0));
}
/* point and normal on triangle */
ccl_device_inline void triangle_point_normal(KernelGlobals *kg, int object, int prim, float u, float v, float3 *P, float3 *Ng, int *shader)
{
/* load triangle vertices */
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
float3 v0 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.x)));
float3 v1 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.y)));
float3 v2 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.z)));
/* compute point */
float t = 1.0f - u - v;
*P = (u*v0 + v*v1 + t*v2);
/* get object flags, instance-aware */
int object_flag = kernel_tex_fetch(__object_flag, object >= 0 ? object : ~object);
/* compute normal */
if(object_flag & SD_NEGATIVE_SCALE_APPLIED)
*Ng = normalize(cross(v2 - v0, v1 - v0));
else
*Ng = normalize(cross(v1 - v0, v2 - v0));
/* shader`*/
*shader = kernel_tex_fetch(__tri_shader, prim);
}
/* Triangle vertex locations */
ccl_device_inline void triangle_vertices(KernelGlobals *kg, int prim, float3 P[3])
{
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
P[0] = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.x)));
P[1] = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.y)));
P[2] = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.z)));
}
/* Interpolate smooth vertex normal from vertices */
ccl_device_inline float3 triangle_smooth_normal(KernelGlobals *kg, int prim, float u, float v)
{
/* load triangle vertices */
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
float3 n0 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, __float_as_int(tri_vindex.x)));
float3 n1 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, __float_as_int(tri_vindex.y)));
float3 n2 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, __float_as_int(tri_vindex.z)));
return normalize((1.0f - u - v)*n2 + u*n0 + v*n1);
}
/* Ray differentials on triangle */
ccl_device_inline void triangle_dPdudv(KernelGlobals *kg, int prim, float3 *dPdu, float3 *dPdv)
{
/* fetch triangle vertex coordinates */
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
float3 p0 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.x)));
float3 p1 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.y)));
float3 p2 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.z)));
/* compute derivatives of P w.r.t. uv */
*dPdu = (p0 - p2);
*dPdv = (p1 - p2);
}
/* Reading attributes on various triangle elements */
ccl_device float triangle_attribute_float(KernelGlobals *kg, const ShaderData *sd, AttributeElement elem, int offset, float *dx, float *dy)
{
if(elem == ATTR_ELEMENT_FACE) {
if(dx) *dx = 0.0f;
if(dy) *dy = 0.0f;
return kernel_tex_fetch(__attributes_float, offset + sd->prim);
}
else if(elem == ATTR_ELEMENT_VERTEX || elem == ATTR_ELEMENT_VERTEX_MOTION) {
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
float f0 = kernel_tex_fetch(__attributes_float, offset + __float_as_int(tri_vindex.x));
float f1 = kernel_tex_fetch(__attributes_float, offset + __float_as_int(tri_vindex.y));
float f2 = kernel_tex_fetch(__attributes_float, offset + __float_as_int(tri_vindex.z));
#ifdef __RAY_DIFFERENTIALS__
if(dx) *dx = sd->du.dx*f0 + sd->dv.dx*f1 - (sd->du.dx + sd->dv.dx)*f2;
if(dy) *dy = sd->du.dy*f0 + sd->dv.dy*f1 - (sd->du.dy + sd->dv.dy)*f2;
#endif
return sd->u*f0 + sd->v*f1 + (1.0f - sd->u - sd->v)*f2;
}
else if(elem == ATTR_ELEMENT_CORNER) {
int tri = offset + sd->prim*3;
float f0 = kernel_tex_fetch(__attributes_float, tri + 0);
float f1 = kernel_tex_fetch(__attributes_float, tri + 1);
float f2 = kernel_tex_fetch(__attributes_float, tri + 2);
#ifdef __RAY_DIFFERENTIALS__
if(dx) *dx = sd->du.dx*f0 + sd->dv.dx*f1 - (sd->du.dx + sd->dv.dx)*f2;
if(dy) *dy = sd->du.dy*f0 + sd->dv.dy*f1 - (sd->du.dy + sd->dv.dy)*f2;
#endif
return sd->u*f0 + sd->v*f1 + (1.0f - sd->u - sd->v)*f2;
}
else {
if(dx) *dx = 0.0f;
if(dy) *dy = 0.0f;
return 0.0f;
}
}
ccl_device float3 triangle_attribute_float3(KernelGlobals *kg, const ShaderData *sd, AttributeElement elem, int offset, float3 *dx, float3 *dy)
{
if(elem == ATTR_ELEMENT_FACE) {
if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);
return float4_to_float3(kernel_tex_fetch(__attributes_float3, offset + sd->prim));
}
else if(elem == ATTR_ELEMENT_VERTEX || elem == ATTR_ELEMENT_VERTEX_MOTION) {
float4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
float3 f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, offset + __float_as_int(tri_vindex.x)));
float3 f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, offset + __float_as_int(tri_vindex.y)));
float3 f2 = float4_to_float3(kernel_tex_fetch(__attributes_float3, offset + __float_as_int(tri_vindex.z)));
#ifdef __RAY_DIFFERENTIALS__
if(dx) *dx = sd->du.dx*f0 + sd->dv.dx*f1 - (sd->du.dx + sd->dv.dx)*f2;
if(dy) *dy = sd->du.dy*f0 + sd->dv.dy*f1 - (sd->du.dy + sd->dv.dy)*f2;
#endif
return sd->u*f0 + sd->v*f1 + (1.0f - sd->u - sd->v)*f2;
}
else if(elem == ATTR_ELEMENT_CORNER || elem == ATTR_ELEMENT_CORNER_BYTE) {
int tri = offset + sd->prim*3;
float3 f0, f1, f2;
if(elem == ATTR_ELEMENT_CORNER) {
f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, tri + 0));
f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, tri + 1));
f2 = float4_to_float3(kernel_tex_fetch(__attributes_float3, tri + 2));
}
else {
f0 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, tri + 0));
f1 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, tri + 1));
f2 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, tri + 2));
}
#ifdef __RAY_DIFFERENTIALS__
if(dx) *dx = sd->du.dx*f0 + sd->dv.dx*f1 - (sd->du.dx + sd->dv.dx)*f2;
if(dy) *dy = sd->du.dy*f0 + sd->dv.dy*f1 - (sd->du.dy + sd->dv.dy)*f2;
#endif
return sd->u*f0 + sd->v*f1 + (1.0f - sd->u - sd->v)*f2;
}
else {
if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);
return make_float3(0.0f, 0.0f, 0.0f);
}
}
CCL_NAMESPACE_END
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