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To tie this all together, here's some pseudo code to convey the RixIntegrator requirements for the tracing of volume-aware indirect rays:
| Code Block | ||
|---|---|---|
| ||
// ictx is a RixIntegratorContext associated with primary camera rays
// sctx is a RixShadingContext associated with a group of hit points
// requiring shading. We are tracing the indirect rays traced by the
// the sctx. The bxdf GenerateSamples method has already been executed
// on the sctx to determine the directions of these rays as well as
// whether or not the rays transmit into the surface.
if (!sctx->HasVolume(k_AnyVolume))
ictx->GetNearestHits(...);
else
// Group the rays into 2 bundles: transmit and reflect.
// This can be accomplished by checking the lobeSampled.GetTransmit()
// flag on the ray
RixVolumeIntegrator *volint;
if( transRays)
{
volint = sctx->BeginOppositeVol(transRays.size(), transRays);
if(volint)
volint->GetNearestHits(...);
sctx->EndVolume(volint);
else
ictx->GetNearestHits(...);
}
if (reflRays)
{
volint = sctx->BeginIncidentVol(reflRays.size(), reflRays);
if(volint)
volint->GetNearestHits(...);
sctx->EndVolume(volint);
else
ictx->GetNearestHits(...);
} |
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Volume Closures
Similar to RixBxdf, RixVolumeIntegrators are closures that are created by a subclass of RixBxdfFactory - in this case, by a call to RixBxdfFactory::BeginInterior(). At the time that BeginInterior() is called, a shading context is bound to the RixVolumeIntegrator. Pattern graph evaluation via EvalParam() may occur during BeginInterior() to evaluate any needed inputs to the volume integrator that may be used by GetNearestHits() or GetTransmission(). Hence, any outputs from these pattern graph evaluations should be saved explicitly by the plugin until these routines (GetNearestHits()/GetTransmission) are called (hence our use of the term closure).
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