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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.
*/
CCL_NAMESPACE_BEGIN
#ifdef __SHADER_RAYTRACE__
/* Bevel shader averaging normals from nearby surfaces.
*
* Sampling strategy from: BSSRDF Importance Sampling, SIGGRAPH 2013
* http://library.imageworks.com/pdfs/imageworks-library-BSSRDF-sampling.pdf
*/
ccl_device_noinline float3 svm_bevel(KernelGlobals *kg,
ShaderData *sd,
ccl_addr_space PathState *state,
float radius,
int num_samples)
{
/* Early out if no sampling needed. */
if (radius <= 0.0f || num_samples < 1 || sd->object == OBJECT_NONE) {
return sd->N;
}
/* Can't raytrace from shaders like displacement, before BVH exists. */
if (kernel_data.bvh.bvh_layout == BVH_LAYOUT_NONE) {
return sd->N;
}
/* Don't bevel for blurry indirect rays. */
if (state->min_ray_pdf < 8.0f) {
return sd->N;
}
/* Setup for multi intersection. */
LocalIntersection isect;
uint lcg_state = lcg_state_init_addrspace(state, 0x64c6a40e);
/* Sample normals from surrounding points on surface. */
float3 sum_N = make_float3(0.0f, 0.0f, 0.0f);
for (int sample = 0; sample < num_samples; sample++) {
float disk_u, disk_v;
path_branched_rng_2D(
kg, state->rng_hash, state, sample, num_samples, PRNG_BEVEL_U, &disk_u, &disk_v);
/* Pick random axis in local frame and point on disk. */
float3 disk_N, disk_T, disk_B;
float pick_pdf_N, pick_pdf_T, pick_pdf_B;
disk_N = sd->Ng;
make_orthonormals(disk_N, &disk_T, &disk_B);
float axisu = disk_u;
if (axisu < 0.5f) {
pick_pdf_N = 0.5f;
pick_pdf_T = 0.25f;
pick_pdf_B = 0.25f;
disk_u *= 2.0f;
}
else if (axisu < 0.75f) {
float3 tmp = disk_N;
disk_N = disk_T;
disk_T = tmp;
pick_pdf_N = 0.25f;
pick_pdf_T = 0.5f;
pick_pdf_B = 0.25f;
disk_u = (disk_u - 0.5f) * 4.0f;
}
else {
float3 tmp = disk_N;
disk_N = disk_B;
disk_B = tmp;
pick_pdf_N = 0.25f;
pick_pdf_T = 0.25f;
pick_pdf_B = 0.5f;
disk_u = (disk_u - 0.75f) * 4.0f;
}
/* Sample point on disk. */
float phi = M_2PI_F * disk_u;
float disk_r = disk_v;
float disk_height;
/* Perhaps find something better than Cubic BSSRDF, but happens to work well. */
bssrdf_cubic_sample(radius, 0.0f, disk_r, &disk_r, &disk_height);
float3 disk_P = (disk_r * cosf(phi)) * disk_T + (disk_r * sinf(phi)) * disk_B;
/* Create ray. */
Ray *ray = &isect.ray;
ray->P = sd->P + disk_N * disk_height + disk_P;
ray->D = -disk_N;
ray->t = 2.0f * disk_height;
ray->dP = sd->dP;
ray->dD = differential3_zero();
ray->time = sd->time;
/* Intersect with the same object. if multiple intersections are found it
* will use at most LOCAL_MAX_HITS hits, a random subset of all hits. */
scene_intersect_local(kg, ray, &isect, sd->object, &lcg_state, LOCAL_MAX_HITS);
int num_eval_hits = min(isect.num_hits, LOCAL_MAX_HITS);
for (int hit = 0; hit < num_eval_hits; hit++) {
/* Quickly retrieve P and Ng without setting up ShaderData. */
float3 hit_P;
if (sd->type & PRIMITIVE_TRIANGLE) {
hit_P = triangle_refine_local(kg, sd, &isect.hits[hit], ray);
}
# ifdef __OBJECT_MOTION__
else if (sd->type & PRIMITIVE_MOTION_TRIANGLE) {
float3 verts[3];
motion_triangle_vertices(
kg, sd->object, kernel_tex_fetch(__prim_index, isect.hits[hit].prim), sd->time, verts);
hit_P = motion_triangle_refine_local(kg, sd, &isect.hits[hit], ray, verts);
}
# endif /* __OBJECT_MOTION__ */
/* Get geometric normal. */
float3 hit_Ng = isect.Ng[hit];
int object = (isect.hits[hit].object == OBJECT_NONE) ?
kernel_tex_fetch(__prim_object, isect.hits[hit].prim) :
isect.hits[hit].object;
int object_flag = kernel_tex_fetch(__object_flag, object);
if (object_flag & SD_OBJECT_NEGATIVE_SCALE_APPLIED) {
hit_Ng = -hit_Ng;
}
/* Compute smooth normal. */
float3 N = hit_Ng;
int prim = kernel_tex_fetch(__prim_index, isect.hits[hit].prim);
int shader = kernel_tex_fetch(__tri_shader, prim);
if (shader & SHADER_SMOOTH_NORMAL) {
float u = isect.hits[hit].u;
float v = isect.hits[hit].v;
if (sd->type & PRIMITIVE_TRIANGLE) {
N = triangle_smooth_normal(kg, N, prim, u, v);
}
# ifdef __OBJECT_MOTION__
else if (sd->type & PRIMITIVE_MOTION_TRIANGLE) {
N = motion_triangle_smooth_normal(kg, N, sd->object, prim, u, v, sd->time);
}
# endif /* __OBJECT_MOTION__ */
}
/* Transform normals to world space. */
if (!(object_flag & SD_OBJECT_TRANSFORM_APPLIED)) {
object_normal_transform(kg, sd, &N);
object_normal_transform(kg, sd, &hit_Ng);
}
/* Probability densities for local frame axes. */
float pdf_N = pick_pdf_N * fabsf(dot(disk_N, hit_Ng));
float pdf_T = pick_pdf_T * fabsf(dot(disk_T, hit_Ng));
float pdf_B = pick_pdf_B * fabsf(dot(disk_B, hit_Ng));
/* Multiple importance sample between 3 axes, power heuristic
* found to be slightly better than balance heuristic. pdf_N
* in the MIS weight and denominator cancelled out. */
float w = pdf_N / (sqr(pdf_N) + sqr(pdf_T) + sqr(pdf_B));
if (isect.num_hits > LOCAL_MAX_HITS) {
w *= isect.num_hits / (float)LOCAL_MAX_HITS;
}
/* Real distance to sampled point. */
float r = len(hit_P - sd->P);
/* Compute weight. */
float pdf = bssrdf_cubic_pdf(radius, 0.0f, r);
float disk_pdf = bssrdf_cubic_pdf(radius, 0.0f, disk_r);
w *= pdf / disk_pdf;
/* Sum normal and weight. */
sum_N += w * N;
}
}
/* Normalize. */
float3 N = safe_normalize(sum_N);
return is_zero(N) ? sd->N : (sd->flag & SD_BACKFACING) ? -N : N;
}
ccl_device void svm_node_bevel(
KernelGlobals *kg, ShaderData *sd, ccl_addr_space PathState *state, float *stack, uint4 node)
{
uint num_samples, radius_offset, normal_offset, out_offset;
svm_unpack_node_uchar4(node.y, &num_samples, &radius_offset, &normal_offset, &out_offset);
float radius = stack_load_float(stack, radius_offset);
float3 bevel_N = svm_bevel(kg, sd, state, radius, num_samples);
if (stack_valid(normal_offset)) {
/* Preserve input normal. */
float3 ref_N = stack_load_float3(stack, normal_offset);
bevel_N = normalize(ref_N + (bevel_N - sd->N));
}
stack_store_float3(stack, out_offset, bevel_N);
}
#endif /* __SHADER_RAYTRACE__ */
CCL_NAMESPACE_END
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