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disable adjoint BSDF for shading normals in the particle tracer, reasoning given in the comment

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Wenzel Jakob 2012-10-18 12:39:13 -04:00
parent ae3f196dd1
commit 7a81c2ae4c
1 changed files with 17 additions and 0 deletions
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17
src/librender/particleproc.cpp
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@ -219,10 +219,27 @@ void ParticleTracer::process(const WorkUnit *workUnit, WorkResult *workResult,
if (its.isMediumTransition()) if (its.isMediumTransition())
medium = its.getTargetMedium(woDotGeoN); medium = its.getTargetMedium(woDotGeoN);
#if 0
/* This is somewhat unfortunate: for accuracy, we'd really want the
correction factor below to match the path tracing interpretation
of a scene with surface normals. However, this factor can become
extremely large, which adds unacceptable variance to output
renderings.
So for now, it is disabled. The adjoint particle tracer and the
photon mapping variants still use this factor for the last
bounce -- just not for the intermediate ones, which introduces
a small (though in practice not noticeable) amount of error. This
is also what the implementation of SPPM by Toshiya Hachisuka does.
Ultimately, we'll need better adjoint BSDF sampling strategies
that incorporate these extra terms */
/* Adjoint BSDF for shading normals -- [Veach, p. 155] */ /* Adjoint BSDF for shading normals -- [Veach, p. 155] */
throughput *= std::abs( throughput *= std::abs(
(Frame::cosTheta(bRec.wi) * woDotGeoN)/ (Frame::cosTheta(bRec.wi) * woDotGeoN)/
(Frame::cosTheta(bRec.wo) * wiDotGeoN)); (Frame::cosTheta(bRec.wo) * wiDotGeoN));
#endif
ray.setOrigin(its.p); ray.setOrigin(its.p);
ray.setDirection(wo); ray.setDirection(wo);