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blender/intern/cycles/kernel/geom/geom_triangle.h
Mikhail Matrosov 9c6a382f95 Cycles: reduce shadow terminator artifacts 
Offset rays from the flat surface to match where they would be for a smooth
surface as specified by the normals. In the shading panel there is now a
Shading Offset (existing option) and Geometry Offset (new).

The Geometry Offset works as follows:
* 0: disabled
* 0.001: only terminated triangles (normal points to the light, geometry
  doesn't) are affected
* 0.1 (default): triangles at grazing angles are affected, and the effect
  fades out
* 1: all triangles are affected

Limitations:
* The artifact is still visible in some cases, it could be that some quads
  require to be treated specifically as quads.
* Inconsistent normals cause artifacts.
* If small objects cast shadows to a big low poly surface, the shadows can
  appear to be in a wrong place - because the surface moved slightly above
  the geometry. This can be noticed only at grazing angles to light.
* Approximated surfaces of two non-intersecting low-poly objects can overlap
  that causes off-the-wall shadows.

Generally, using one or a few levels of subdivision can get rid of artifacts
faster than before.

Differential Revision: https://developer.blender.org/D11065
2021-06-28 14:05:22 +02:00

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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.
*/
/* 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 */
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
const float3 v0 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
const float3 v1 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
const float3 v2 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
/* return normal */
if (sd->object_flag & SD_OBJECT_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 */
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
float3 v0 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
float3 v1 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
float3 v2 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
/* compute point */
float t = 1.0f - u - v;
*P = (u * v0 + v * v1 + t * v2);
/* get object flags */
int object_flag = kernel_tex_fetch(__object_flag, object);
/* compute normal */
if (object_flag & SD_OBJECT_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])
{
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
P[0] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
P[1] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
P[2] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
}
/* Triangle vertex locations and vertex normals */
ccl_device_inline void triangle_vertices_and_normals(KernelGlobals *kg, int prim, float3 P[3], float3 N[3])
{
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
P[0] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
P[1] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
P[2] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
N[0] = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.x));
N[1] = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.y));
N[2] = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.z));
}
/* Interpolate smooth vertex normal from vertices */
ccl_device_inline float3
triangle_smooth_normal(KernelGlobals *kg, float3 Ng, int prim, float u, float v)
{
/* load triangle vertices */
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
float3 n0 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.x));
float3 n1 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.y));
float3 n2 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.z));
float3 N = safe_normalize((1.0f - u - v) * n2 + u * n0 + v * n1);
return is_zero(N) ? Ng : N;
}
/* Ray differentials on triangle */
ccl_device_inline void triangle_dPdudv(KernelGlobals *kg,
int prim,
ccl_addr_space float3 *dPdu,
ccl_addr_space float3 *dPdv)
{
/* fetch triangle vertex coordinates */
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
const float3 p0 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
const float3 p1 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
const float3 p2 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
/* 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, const AttributeDescriptor desc, float *dx, float *dy)
{
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION | ATTR_ELEMENT_CORNER)) {
float f0, f1, f2;
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION)) {
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
f0 = kernel_tex_fetch(__attributes_float, desc.offset + tri_vindex.x);
f1 = kernel_tex_fetch(__attributes_float, desc.offset + tri_vindex.y);
f2 = kernel_tex_fetch(__attributes_float, desc.offset + tri_vindex.z);
}
else {
const int tri = desc.offset + sd->prim * 3;
f0 = kernel_tex_fetch(__attributes_float, tri + 0);
f1 = kernel_tex_fetch(__attributes_float, tri + 1);
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 {
#ifdef __RAY_DIFFERENTIALS__
if (dx)
*dx = 0.0f;
if (dy)
*dy = 0.0f;
#endif
if (desc.element & (ATTR_ELEMENT_FACE | ATTR_ELEMENT_OBJECT | ATTR_ELEMENT_MESH)) {
const int offset = (desc.element == ATTR_ELEMENT_FACE) ? desc.offset + sd->prim :
desc.offset;
return kernel_tex_fetch(__attributes_float, offset);
}
else {
return 0.0f;
}
}
}
ccl_device float2 triangle_attribute_float2(KernelGlobals *kg,
const ShaderData *sd,
const AttributeDescriptor desc,
float2 *dx,
float2 *dy)
{
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION | ATTR_ELEMENT_CORNER)) {
float2 f0, f1, f2;
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION)) {
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
f0 = kernel_tex_fetch(__attributes_float2, desc.offset + tri_vindex.x);
f1 = kernel_tex_fetch(__attributes_float2, desc.offset + tri_vindex.y);
f2 = kernel_tex_fetch(__attributes_float2, desc.offset + tri_vindex.z);
}
else {
const int tri = desc.offset + sd->prim * 3;
f0 = kernel_tex_fetch(__attributes_float2, tri + 0);
f1 = kernel_tex_fetch(__attributes_float2, tri + 1);
f2 = kernel_tex_fetch(__attributes_float2, 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 {
#ifdef __RAY_DIFFERENTIALS__
if (dx)
*dx = make_float2(0.0f, 0.0f);
if (dy)
*dy = make_float2(0.0f, 0.0f);
#endif
if (desc.element & (ATTR_ELEMENT_FACE | ATTR_ELEMENT_OBJECT | ATTR_ELEMENT_MESH)) {
const int offset = (desc.element == ATTR_ELEMENT_FACE) ? desc.offset + sd->prim :
desc.offset;
return kernel_tex_fetch(__attributes_float2, offset);
}
else {
return make_float2(0.0f, 0.0f);
}
}
}
ccl_device float3 triangle_attribute_float3(KernelGlobals *kg,
const ShaderData *sd,
const AttributeDescriptor desc,
float3 *dx,
float3 *dy)
{
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION | ATTR_ELEMENT_CORNER)) {
float3 f0, f1, f2;
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION)) {
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.x));
f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.y));
f2 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.z));
}
else {
const int tri = desc.offset + sd->prim * 3;
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));
}
#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 {
#ifdef __RAY_DIFFERENTIALS__
if (dx)
*dx = make_float3(0.0f, 0.0f, 0.0f);
if (dy)
*dy = make_float3(0.0f, 0.0f, 0.0f);
#endif
if (desc.element & (ATTR_ELEMENT_FACE | ATTR_ELEMENT_OBJECT | ATTR_ELEMENT_MESH)) {
const int offset = (desc.element == ATTR_ELEMENT_FACE) ? desc.offset + sd->prim :
desc.offset;
return float4_to_float3(kernel_tex_fetch(__attributes_float3, offset));
}
else {
return make_float3(0.0f, 0.0f, 0.0f);
}
}
}
ccl_device float4 triangle_attribute_float4(KernelGlobals *kg,
const ShaderData *sd,
const AttributeDescriptor desc,
float4 *dx,
float4 *dy)
{
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION | ATTR_ELEMENT_CORNER |
ATTR_ELEMENT_CORNER_BYTE)) {
float4 f0, f1, f2;
if (desc.element & (ATTR_ELEMENT_VERTEX | ATTR_ELEMENT_VERTEX_MOTION)) {
const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
f0 = kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.x);
f1 = kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.y);
f2 = kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.z);
}
else {
const int tri = desc.offset + sd->prim * 3;
if (desc.element == ATTR_ELEMENT_CORNER) {
f0 = kernel_tex_fetch(__attributes_float3, tri + 0);
f1 = kernel_tex_fetch(__attributes_float3, tri + 1);
f2 = kernel_tex_fetch(__attributes_float3, tri + 2);
}
else {
f0 = color_srgb_to_linear_v4(
color_uchar4_to_float4(kernel_tex_fetch(__attributes_uchar4, tri + 0)));
f1 = color_srgb_to_linear_v4(
color_uchar4_to_float4(kernel_tex_fetch(__attributes_uchar4, tri + 1)));
f2 = color_srgb_to_linear_v4(
color_uchar4_to_float4(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 {
#ifdef __RAY_DIFFERENTIALS__
if (dx)
*dx = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
if (dy)
*dy = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
#endif
if (desc.element & (ATTR_ELEMENT_FACE | ATTR_ELEMENT_OBJECT | ATTR_ELEMENT_MESH)) {
const int offset = (desc.element == ATTR_ELEMENT_FACE) ? desc.offset + sd->prim :
desc.offset;
return kernel_tex_fetch(__attributes_float3, offset);
}
else {
return make_float4(0.0f, 0.0f, 0.0f, 0.0f);
}
}
}
CCL_NAMESPACE_END
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