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/*
* Copyright 2014, 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/Ray intersections.
*
* For BVH ray intersection we use a precomputed triangle storage to accelerate
* intersection at the cost of more memory usage.
*/
CCL_NAMESPACE_BEGIN
/* Ray-Triangle intersection for BVH traversal
*
* Sven Woop
* Watertight Ray/Triangle Intersection
*
* http://jcgt.org/published/0002/01/05/paper.pdf
*/
ccl_device_inline bool triangle_intersect(KernelGlobals *kg,
const TriangleIsectPrecalc *isect_precalc,
Intersection *isect,
float3 P,
uint visibility,
int object,
int prim_addr)
{
const uint tri_vindex = kernel_tex_fetch(__prim_tri_index, prim_addr);
#if defined(__KERNEL_AVX2__) && defined(__KERNEL_SSE__)
const ssef *ssef_verts = (ssef*)&kg->__prim_tri_verts.data[tri_vindex];
#else
const float4 tri_a = kernel_tex_fetch(__prim_tri_verts, tri_vindex+0),
tri_b = kernel_tex_fetch(__prim_tri_verts, tri_vindex+1),
tri_c = kernel_tex_fetch(__prim_tri_verts, tri_vindex+2);
#endif
float t, u, v;
if(ray_triangle_intersect(isect_precalc,
P, isect->t,
#if defined(__KERNEL_AVX2__) && defined(__KERNEL_SSE__)
ssef_verts,
#else
float4_to_float3(tri_a),
float4_to_float3(tri_b),
float4_to_float3(tri_c),
#endif
&u, &v, &t))
{
#ifdef __VISIBILITY_FLAG__
/* Visibility flag test. we do it here under the assumption
* that most triangles are culled by node flags.
*/
if(kernel_tex_fetch(__prim_visibility, prim_addr) & visibility)
#endif
{
isect->prim = prim_addr;
isect->object = object;
isect->type = PRIMITIVE_TRIANGLE;
isect->u = u;
isect->v = v;
isect->t = t;
return true;
}
}
return false;
}
/* Special ray intersection routines for subsurface scattering. In that case we
* only want to intersect with primitives in the same object, and if case of
* multiple hits we pick a single random primitive as the intersection point.
*/
#ifdef __SUBSURFACE__
ccl_device_inline void triangle_intersect_subsurface(
KernelGlobals *kg,
const TriangleIsectPrecalc *isect_precalc,
SubsurfaceIntersection *ss_isect,
float3 P,
int object,
int prim_addr,
float tmax,
uint *lcg_state,
int max_hits)
{
const uint tri_vindex = kernel_tex_fetch(__prim_tri_index, prim_addr);
#if defined(__KERNEL_AVX2__) && defined(__KERNEL_SSE__)
const ssef *ssef_verts = (ssef*)&kg->__prim_tri_verts.data[tri_vindex];
#else
const float3 tri_a = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex+0)),
tri_b = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex+1)),
tri_c = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex+2));
#endif
float t, u, v;
if(!ray_triangle_intersect(isect_precalc,
P, tmax,
#if defined(__KERNEL_AVX2__) && defined(__KERNEL_SSE__)
ssef_verts,
#else
tri_a,
tri_b,
tri_c,
#endif
&u, &v, &t))
{
return;
}
for(int i = min(max_hits, ss_isect->num_hits) - 1; i >= 0; --i) {
if(ss_isect->hits[i].t == t) {
return;
}
}
ss_isect->num_hits++;
int hit;
if(ss_isect->num_hits <= max_hits) {
hit = ss_isect->num_hits - 1;
}
else {
/* reservoir sampling: if we are at the maximum number of
* hits, randomly replace element or skip it */
hit = lcg_step_uint(lcg_state) % ss_isect->num_hits;
if(hit >= max_hits)
return;
}
/* record intersection */
Intersection *isect = &ss_isect->hits[hit];
isect->prim = prim_addr;
isect->object = object;
isect->type = PRIMITIVE_TRIANGLE;
isect->u = u;
isect->v = v;
isect->t = t;
/* Record geometric normal. */
/* TODO(sergey): Check whether it's faster to re-use ssef verts. */
#if defined(__KERNEL_AVX2__) && defined(__KERNEL_SSE__)
const float3 tri_a = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex+0)),
tri_b = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex+1)),
tri_c = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex+2));
#endif
ss_isect->Ng[hit] = normalize(cross(tri_b - tri_a, tri_c - tri_a));
}
#endif
/* Refine triangle intersection to more precise hit point. For rays that travel
* far the precision is often not so good, this reintersects the primitive from
* a closer distance. */
/* Reintersections uses the paper:
*
* Tomas Moeller
* Fast, minimum storage ray/triangle intersection
* http://www.cs.virginia.edu/~gfx/Courses/2003/ImageSynthesis/papers/Acceleration/Fast%20MinimumStorage%20RayTriangle%20Intersection.pdf
*/
ccl_device_inline float3 triangle_refine(KernelGlobals *kg,
ShaderData *sd,
const Intersection *isect,
const Ray *ray)
{
float3 P = ray->P;
float3 D = ray->D;
float t = isect->t;
#ifdef __INTERSECTION_REFINE__
if(isect->object != OBJECT_NONE) {
if(UNLIKELY(t == 0.0f)) {
return P;
}
# ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_itfm;
# else
Transform tfm = object_fetch_transform(kg, isect->object, OBJECT_INVERSE_TRANSFORM);
# endif
P = transform_point(&tfm, P);
D = transform_direction(&tfm, D*t);
D = normalize_len(D, &t);
}
P = P + D*t;
const uint tri_vindex = kernel_tex_fetch(__prim_tri_index, isect->prim);
const float4 tri_a = kernel_tex_fetch(__prim_tri_verts, tri_vindex+0),
tri_b = kernel_tex_fetch(__prim_tri_verts, tri_vindex+1),
tri_c = kernel_tex_fetch(__prim_tri_verts, tri_vindex+2);
float3 edge1 = make_float3(tri_a.x - tri_c.x, tri_a.y - tri_c.y, tri_a.z - tri_c.z);
float3 edge2 = make_float3(tri_b.x - tri_c.x, tri_b.y - tri_c.y, tri_b.z - tri_c.z);
float3 tvec = make_float3(P.x - tri_c.x, P.y - tri_c.y, P.z - tri_c.z);
float3 qvec = cross(tvec, edge1);
float3 pvec = cross(D, edge2);
float det = dot(edge1, pvec);
if(det != 0.0f) {
/* If determinant is zero it means ray lies in the plane of
* the triangle. It is possible in theory due to watertight
* nature of triangle intersection. For such cases we simply
* don't refine intersection hoping it'll go all fine.
*/
float rt = dot(edge2, qvec) / det;
P = P + D*rt;
}
if(isect->object != OBJECT_NONE) {
# ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_tfm;
# else
Transform tfm = object_fetch_transform(kg, isect->object, OBJECT_TRANSFORM);
# endif
P = transform_point(&tfm, P);
}
return P;
#else
return P + D*t;
#endif
}
/* Same as above, except that isect->t is assumed to be in object space for
* instancing.
*/
ccl_device_inline float3 triangle_refine_subsurface(KernelGlobals *kg,
ShaderData *sd,
const Intersection *isect,
const Ray *ray)
{
float3 P = ray->P;
float3 D = ray->D;
float t = isect->t;
if(isect->object != OBJECT_NONE) {
#ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_itfm;
#else
Transform tfm = object_fetch_transform(kg,
isect->object,
OBJECT_INVERSE_TRANSFORM);
#endif
P = transform_point(&tfm, P);
D = transform_direction(&tfm, D);
D = normalize(D);
}
P = P + D*t;
#ifdef __INTERSECTION_REFINE__
const uint tri_vindex = kernel_tex_fetch(__prim_tri_index, isect->prim);
const float4 tri_a = kernel_tex_fetch(__prim_tri_verts, tri_vindex+0),
tri_b = kernel_tex_fetch(__prim_tri_verts, tri_vindex+1),
tri_c = kernel_tex_fetch(__prim_tri_verts, tri_vindex+2);
float3 edge1 = make_float3(tri_a.x - tri_c.x, tri_a.y - tri_c.y, tri_a.z - tri_c.z);
float3 edge2 = make_float3(tri_b.x - tri_c.x, tri_b.y - tri_c.y, tri_b.z - tri_c.z);
float3 tvec = make_float3(P.x - tri_c.x, P.y - tri_c.y, P.z - tri_c.z);
float3 qvec = cross(tvec, edge1);
float3 pvec = cross(D, edge2);
float det = dot(edge1, pvec);
if(det != 0.0f) {
/* If determinant is zero it means ray lies in the plane of
* the triangle. It is possible in theory due to watertight
* nature of triangle intersection. For such cases we simply
* don't refine intersection hoping it'll go all fine.
*/
float rt = dot(edge2, qvec) / det;
P = P + D*rt;
}
#endif /* __INTERSECTION_REFINE__ */
if(isect->object != OBJECT_NONE) {
#ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_tfm;
#else
Transform tfm = object_fetch_transform(kg,
isect->object,
OBJECT_TRANSFORM);
#endif
P = transform_point(&tfm, P);
}
return P;
}
CCL_NAMESPACE_END
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