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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
/* Motion Triangle Primitive
*
* These are stored as regular triangles, plus extra positions and normals at
* times other than the frame center. Computing the triangle vertex positions
* or normals at a given ray time is a matter of interpolation of the two steps
* between which the ray time lies.
*
* The extra positions and normals are stored as ATTR_STD_MOTION_VERTEX_POSITION
* and ATTR_STD_MOTION_VERTEX_NORMAL mesh attributes.
*/
#pragma once
CCL_NAMESPACE_BEGIN
/* Setup of motion triangle specific parts of ShaderData, moved into this one
* function to more easily share computation of interpolated positions and
* normals */
/* return 3 triangle vertex normals */
ccl_device_noinline void motion_triangle_shader_setup(KernelGlobals kg,
ccl_private ShaderData *sd,
const float3 P,
const float3 D,
const float ray_t,
const int isect_object,
const int isect_prim,
bool is_local)
{
/* Get shader. */
sd->shader = kernel_data_fetch(tri_shader, sd->prim);
/* Get motion info. */
/* TODO(sergey): This logic is really similar to motion_triangle_vertices(),
* can we de-duplicate something here?
*/
int numsteps, numverts;
object_motion_info(kg, sd->object, &numsteps, &numverts, NULL);
/* Figure out which steps we need to fetch and their interpolation factor. */
int maxstep = numsteps * 2;
int step = min((int)(sd->time * maxstep), maxstep - 1);
float t = sd->time * maxstep - step;
/* Find attribute. */
int offset = intersection_find_attribute(kg, sd->object, ATTR_STD_MOTION_VERTEX_POSITION);
kernel_assert(offset != ATTR_STD_NOT_FOUND);
/* Fetch vertex coordinates. */
float3 verts[3], next_verts[3];
uint4 tri_vindex = kernel_data_fetch(tri_vindex, sd->prim);
motion_triangle_verts_for_step(kg, tri_vindex, offset, numverts, numsteps, step, verts);
motion_triangle_verts_for_step(kg, tri_vindex, offset, numverts, numsteps, step + 1, next_verts);
/* Interpolate between steps. */
verts[0] = (1.0f - t) * verts[0] + t * next_verts[0];
verts[1] = (1.0f - t) * verts[1] + t * next_verts[1];
verts[2] = (1.0f - t) * verts[2] + t * next_verts[2];
/* Compute refined position. */
sd->P = motion_triangle_point_from_uv(kg, sd, isect_object, isect_prim, sd->u, sd->v, verts);
/* Compute face normal. */
float3 Ng;
if (sd->object_flag & SD_OBJECT_NEGATIVE_SCALE_APPLIED) {
Ng = normalize(cross(verts[2] - verts[0], verts[1] - verts[0]));
}
else {
Ng = normalize(cross(verts[1] - verts[0], verts[2] - verts[0]));
}
sd->Ng = Ng;
sd->N = Ng;
/* Compute derivatives of P w.r.t. uv. */
#ifdef __DPDU__
sd->dPdu = (verts[0] - verts[2]);
sd->dPdv = (verts[1] - verts[2]);
#endif
/* Compute smooth normal. */
if (sd->shader & SHADER_SMOOTH_NORMAL) {
/* Find attribute. */
int offset = intersection_find_attribute(kg, sd->object, ATTR_STD_MOTION_VERTEX_NORMAL);
kernel_assert(offset != ATTR_STD_NOT_FOUND);
/* Fetch vertex coordinates. */
float3 normals[3], next_normals[3];
motion_triangle_normals_for_step(kg, tri_vindex, offset, numverts, numsteps, step, normals);
motion_triangle_normals_for_step(
kg, tri_vindex, offset, numverts, numsteps, step + 1, next_normals);
/* Interpolate between steps. */
normals[0] = (1.0f - t) * normals[0] + t * next_normals[0];
normals[1] = (1.0f - t) * normals[1] + t * next_normals[1];
normals[2] = (1.0f - t) * normals[2] + t * next_normals[2];
/* Interpolate between vertices. */
float u = sd->u;
float v = sd->v;
float w = 1.0f - u - v;
sd->N = (u * normals[0] + v * normals[1] + w * normals[2]);
}
}
CCL_NAMESPACE_END
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