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Parameters

ParameterDescription 
maxPathLengthControls the absolute upper bound on the maximum ray depth. A value of 1 for this parameter will allow direct illumination only, while a value of 4 will permit up to 3 bounces of global illumination. Default value is 10.jksdbjksdbgfsjkbdfksjdbgksjdbgk
sampleModeControls the strategy for how indirect ray counts are apportioned between diffuse vs. glossy vs. specular Bxdf lobes. Valid values for this parameter are: "bxdf" or "manual". If "sampleMode" is set to "bxdf", then the Bxdf is responsible for balancing the number of indirect rays that will be spawned at each camera hit point between the diffuse vs. glossy vs. specular lobes, and the total number of indirect rays spawned at each camera hit point will be controlled by the numIndirectSamples parameter. If"sampleMode" is set to "manual" the user is responsible for explicitly specifying the number of indirect rays to spawn per Bxdf lobe at each camera hit point via the numDiffuseSamples, numSpecularSamples, numSubsurfaceSamples, andnumRefractionSamples parameters. The default is "bxdf". 
numLightSamples Controls the number of light samples for direct illumination per camera hit point. The default is 1. 
numBxdfSamplesControls the number of Bxdf samples for direct illumination per camera hit point. The default is 1. 
numIndirectSamplesWhen sampleMode is set to Bxdf this parameter controls the total number of indirect rays to spawn per camera hit point. WhensampleMode is set to manual the value of this parameter is ignored. The default is 1. 
numDiffuseSamplesWhen sampleMode is set to manual, controls the number of indirect diffuse reflection rays to spawn per camera hit point. Ignored when sampleMode is set to Bxdf. The default is 1. 
numSpecularSamplesWhen sampleMode is set to manual, controls the number of indirect specular/glossy reflection rays to spawn per camera hit point. Ignored when sampleMode is set to Bxdf. The default is 1. 
numSubsurfaceSamplesWhen sampleMode is set to manual, controls the number of subsurface rays to spawn per camera hit point. Ignored whensampleMode is set to Bxdf. The default is 1. 
numRefractionSamplesWhen sampleMode is set to manual, controls the number of refraction/transmission rays to spawn per camera hit point. Ignored when sampleMode is set to "bxdf". The default is 1. 
rouletteDepthControls the ray depth to begin performing Russian Roulette. The default is 4. 
rouletteThresholdControls the path throughput threshold below which to begin performing Russian Roulette. The default is 0.2. 
clampDepthIf a value for the clampLuminance parameter is specified, then clampDepth controls the ray depth at which to begin clamping based on the per-ray luminance. For example, setting this parameter to 2 and also specifying a value of 4 for clampLuminancewill ensure that the luminance of each ray's contribution is no more than 4 for all indirect illumination, without affecting or clamping the direct illumination. The default is 2. 
clampLuminanceBy default the PxrPathTracer integrator clamps the luminance of each per-ray contribution to be at most 10.0. However, it is possible to change this behavior by specifying a different value for the clampLuminance parameter. Specifying a relatively low value for the clampLuminance parameter (for example, between 2 and 20) can greatly speed up convergence and, in many cases, will make PxrPathTracer converge more quickly than the more sophisticated PxrVCM or PxrUPBP integrator. In some cases, indirect illumination lights paths may be noticeably dimmer due to clamping; this may be an acceptable trade-off in certain cases. Setting this parameter to a very large number (such as 1e30) will effectively disable all clamping. The default is 10.0. 
allowCausticsControls whether illumination from caustic light paths (that is, specular illumination onto diffuse surfaces) is allowed or disallowed. The default is 0 (off). 
accumOpacity 
maxContinuationLength

This is an advanced knob for rendering overlapping volumes. Similar to maxPathLength, this controls the upper bound on the maximum ray depth including continuation rays. Any negative value will cause the path tracer to use an empirical heuristic to bound the ray depth. A positive value will override this heuristic and cause the path tracer to use the parameter value directly as the maximum continuation ray depth. Continuation rays are normally produced by volumes when no density exists within subsections of them. If there are many such zero density subsections overlapping then it is possible to quickly hit the maximum continuation depth quickly. If you are rendering a scene with highly overlapping volumes, you might want to adjust this parameter to be generous enough for the ray to exit the scene.

 

Standard AOVs

On top of regular LPE-based AOVs, this integrator outputs a number of standard AOVs typically used by compositors.

DeclarationContentsChannels
color __PworldP in world-space
__Pworld.r : x component
__Pworld.g : y component
__Pworld.b : z component
color __NworldNn in world-space
__Nworld.r : x component
__Nworld.g : y component
__Nworld.b : z component
color __depthMulti-purpose AOV
__depth.r : depth from camera in world-space
__depth.g : height in world-space
__depth.b : geometric facing ratio : abs(Nn.V)
color __stTexture coords
__st.x : s
__st.y : t
__st.z : 0.0
color __PrefReference Position primvar (if available)
__Pref.r : x component
__Pref.g : y component
__Pref.b : z component
color __NrefReference Normal primvar (if available)
__Nref.r : x component
__Nref.g : y component
__Nref.b : z component
color __WPrefReference World Position primvar (if available)
__WPref.r : x component
__WPref.g : y component
__WPref.b : z component
color __WNrefReference World Normal primvar (if available)
__WNref.r : x component
__WNref.g : y component
__WNref.b : z component