Brecht Van Lommel
c18712e868
This to avoids build conflicts with libc++ on FreeBSD, these __ prefixed values are reserved for compilers. I apologize to anyone who has patches or branches and has to go through the pain of merging this change, it may be easiest to do these same replacements in your code and then apply/merge the patch. Ref T37477.
107 lines
2.8 KiB
C
107 lines
2.8 KiB
C
/*
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* Copyright 2011-2013 Blender Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License
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*/
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CCL_NAMESPACE_BEGIN
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/* See "Tracing Ray Differentials", Homan Igehy, 1999. */
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ccl_device void differential_transfer(differential3 *dP_, const differential3 dP, float3 D, const differential3 dD, float3 Ng, float t)
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{
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/* ray differential transfer through homogeneous medium, to
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* compute dPdx/dy at a shading point from the incoming ray */
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float3 tmp = D/dot(D, Ng);
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float3 tmpx = dP.dx + t*dD.dx;
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float3 tmpy = dP.dy + t*dD.dy;
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dP_->dx = tmpx - dot(tmpx, Ng)*tmp;
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dP_->dy = tmpy - dot(tmpy, Ng)*tmp;
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}
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ccl_device void differential_incoming(differential3 *dI, const differential3 dD)
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{
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/* compute dIdx/dy at a shading point, we just need to negate the
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* differential of the ray direction */
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dI->dx = -dD.dx;
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dI->dy = -dD.dy;
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}
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ccl_device void differential_dudv(differential *du, differential *dv, float3 dPdu, float3 dPdv, differential3 dP, float3 Ng)
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{
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/* now we have dPdx/dy from the ray differential transfer, and dPdu/dv
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* from the primitive, we can compute dudx/dy and dvdx/dy. these are
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* mainly used for differentials of arbitrary mesh attributes. */
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/* find most stable axis to project to 2D */
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float xn = fabsf(Ng.x);
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float yn = fabsf(Ng.y);
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float zn = fabsf(Ng.z);
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if(zn < xn || zn < yn) {
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if(yn < xn || yn < zn) {
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dPdu.x = dPdu.y;
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dPdv.x = dPdv.y;
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dP.dx.x = dP.dx.y;
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dP.dy.x = dP.dy.y;
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}
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dPdu.y = dPdu.z;
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dPdv.y = dPdv.z;
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dP.dx.y = dP.dx.z;
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dP.dy.y = dP.dy.z;
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}
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/* using Cramer's rule, we solve for dudx and dvdx in a 2x2 linear system,
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* and the same for dudy and dvdy. the denominator is the same for both
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* solutions, so we compute it only once.
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*
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* dP.dx = dPdu * dudx + dPdv * dvdx;
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* dP.dy = dPdu * dudy + dPdv * dvdy; */
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float det = (dPdu.x*dPdv.y - dPdv.x*dPdu.y);
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if(det != 0.0f)
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det = 1.0f/det;
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du->dx = (dP.dx.x*dPdv.y - dP.dx.y*dPdv.x)*det;
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dv->dx = (dP.dx.y*dPdu.x - dP.dx.x*dPdu.y)*det;
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du->dy = (dP.dy.x*dPdv.y - dP.dy.y*dPdv.x)*det;
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dv->dy = (dP.dy.y*dPdu.x - dP.dy.x*dPdu.y)*det;
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}
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ccl_device differential differential_zero()
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{
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differential d;
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d.dx = 0.0f;
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d.dy = 0.0f;
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return d;
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}
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ccl_device differential3 differential3_zero()
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{
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differential3 d;
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d.dx = make_float3(0.0f, 0.0f, 0.0f);
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d.dy = make_float3(0.0f, 0.0f, 0.0f);
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return d;
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}
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CCL_NAMESPACE_END
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