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LPE EventsDescriptionExample
C
Camera 
<type event 'group'>
Scattering event specified by scattering type, scattering event, or lpe groupC<.[DS]'floor'>[LO] matches all light paths from the floor lpe group
<L.'group'>
Light, i.e. analytic and geometric lightsC[DS]*<L.'key'> matches all light paths from the key light group
O
Emissive object, i.e. camera visible lights and material glowC[DS]*O matches all emissive object light paths
Wildcard  
.
A period will match any relevant event<.D> where the period represents R or T
Scattering Types  
R
ReflectionC<R[DS]>[DS]*[LO] matches all reflected light paths
T
Transmission or refractionC<T[DS]>[DS]*[LO] matches all transmitted light paths
Scattering Events  
D
Diffuse lobes (D1 to D4)CD[DS]*[LO] matches all diffuse light paths
S
Specular/Glossy lobes (S1 to S8)CS[DS]*[LO] matches all specular light paths
U
User lobes used to output material properties (U1 to U12)CU2L matches the camera visible user2 lobe, typically albedo
Grouping  
( )Parentheses allow grouping of a sequence of LPE eventsCDSL, C(DS)L, and CD(SL) are all functionally the same
Alternatives  
|A vertical bar separates alternativesCD|(SD)L matches direct diffuse or specular-diffuse light paths
[ ]Square brackets that match any one of the enclosed eventsC[D2D3]L matches direct diffuse2 or diffuse3 light paths
[^ ]
Square brackets that match any one event not contained within the bracketsC[^D2D3]L matches all light paths besides diffuse2 and diffuse3 (including specular and user)
Qualifiers  
*
An asterisk will match the preceding event zero or more timesC[DS]*[LO] matches all light paths, including emissive
+
A plus sign will match the preceding event one or more timesC[DS]+[LO] matches direct and indirect light paths, but not emissive
{n}
Curly brackets that match the preceding event exactly n timesC<T[DS]>{2}[LO] matches double transmission light paths
{min,}
Curly brackets that match the preceding event min or more timesC[DS]{2,}[LO] matches all indirect light paths
{min,max}
Curly brackets that match the preceding event at least min but not more than max timesC[DS]{0,1}[LO] matches direct and emissive light paths

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Caustics are not included in the built-in list because they overlap with indirectdiffuse lpe:C<RD>[DS]+[<L.>O] However, you can select caustics with the expression lpe:CDS+[<L.>O]  Below you can find an example of the caustics LPE output, Indirect Diffuse, and the difference between them. Note that the Caustics LPE output doesn't capture indirect lighting from object to object, in this case the red cube. You can create the image on the far right with the indirect diffuse minus the caustic result using the following source: lpe:C<RD>D[DS]*[<L.>O]

 

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An LPE group (lpegroup) allows us to specify which objects we want to be use for an LPE channel. The attributes can be added in RenderMan plugins using the software's menu system such as PrmanObjectSettings in Katana.

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Code Block
/prman/lpe/user2                 Albedo,DiffuseAlbedo,SubsurfaceAlbedo,HairAlbedo

Examples

  • In the documentation examples we often use <L.> means Light scattering type with all scattering events. For light group AOVs, using <L.> is required instead in place of L. There's no functional difference.
  • lpe:CD<L.> means camera with diffuse scattering event for light scattering type.
  • lpe:CO means camera with emissive objection (since emissive does not need any light, there is no L).