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| LPE Events | Description | Example |
|---|---|---|
C | Camera | All LPEs must contain a camera event. |
<type event 'group'> | Scattering event specified by scattering type, scattering event, or lpe group | C<.[DS]C<RD'floor'>[LO] matches all light paths diffuse reflections from the floor lpe group |
<L.'group'> | Light, i.e. analytic and geometric lights | C[DS].*<L.'key'> matches all light paths from the key light group |
O | Emissive object, i.e. camera visible lights and material glow | C[DS].*O matches all emissive object light paths |
| Wildcard | ||
. | A period will match any relevant scattering type or event | <.D> where the period represents R or T
|
| Scattering Types | ||
R | Reflection | CR[LO] which is the same as C<R.>[DSLO]> or C<R[DS]*>[LO] matches all reflected light pathsdirect reflection |
T | Transmission or refraction | CT[LO] which is the same as C<T.>[DSLO]> or C<T[DS]*>[LO] matches all transmitted light paths direct transmission |
| Scattering Events | ||
D | Diffuse lobes (D1 to , D2, D3, D4) | CD[DS]*[LO] which is the same as C<.D>[LO] or C<[RT]D>[LO] matches all direct diffuse light paths. |
S | Specular/Glossy lobes (S1 to , S2, S3, S4, S5, S6, S7, S8) | CS[DS]*[LO] which is the same as C<.S>[LO] or C<[RT]S>[LO] matches all specular light paths direct specular |
| User Event | ||
| User lobes used to output material properties, not light transport ( Note: User events must be explicit and will not match wildcards |
|
| Grouping | ||
| ( ) | Parentheses allow grouping of a sequence of LPE events | CDSL, C(DS)L, and CD(SL) are all functionally the sameequivalent |
| Alternatives | ||
| | | A vertical bar separates alternatives | CD|(SD)L matches direct diffuse or specular-diffuse light paths CDL or CSDL |
| [ ] | Square brackets that match any one of the enclosed events | C[D2D3S2 S3 S4]L matches direct diffuse2 or diffuse3 light paths CS2L, CS3L, or CS4L |
[^ ] | Square brackets that match any one event not contained within the brackets | C[^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 times | C[DS].*[LO] matches all light paths, including emissive |
+ | A plus sign will match the preceding event one or more times | C[DS].+[LO] matches direct and indirect light paths, but not emissive |
? | A question mark will match the preceding event zero or one times | C.?[LO] matches direct and emissive light paths |
{n} | Curly brackets that match the preceding event exactly n times | C<T[DS]>CT{2}[LO] matches double transmission light paths |
{min,} | Curly brackets that match the preceding event min or more times | C[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 times | C[DS].{0,12}[LO] matches direct and emissive all light paths with up to one bounce of indirect |
In RIB
To specify an LPE in RIB, reference a DisplayChannel in the Display. This is the most basic way to view what's being output.
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| DisplayChannel | Expression |
|---|---|
color emissive | color lpe:C[<L.>O] |
color directDiffuse | color lpe:C<RD>[<L.>O] |
color indirectDiffuse | color lpe:C<RD>[DS].+[<L.>O] |
color subsurface | color lpe:C<TD>[DS].*[<L.>O] |
color directSpecular | color lpe:C<RS>[<L.>O] |
color indirectSpecular | color lpe:C<RS>[DS].+[<L.>O] |
color transmissive | color lpe:C<TS>[DS].*[<L.>O] |
RenderMan Still Life by Dylan Sisson
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Per-Lobe LPEs
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For advanced workflows that want to separate all scattering lobes into separate AOVs, the below LPE are provided. These capture the light interaction for each lobe, direct and indirect, and store them into separate AOVs. This is useful for tweaking individual effects at the cost of added AOVs and image output. The documentation for PxrMarschner and PxrSurface list these user lobes at the bottom of their page under an Advanced Rollout as it is for informational purposes and not actual operation.
| Note |
|---|
Note that the emissive LPE is repeated below. For materials in RenderMan it's typically called Glow. |
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| DisplayChannel | Expression |
|---|---|
color directDiffuseLobe | color lpe:CD2[<L.>O] |
color indirectDiffuseLobe | color lpe:CD2[DS].+[<L.>O] |
color subsurfaceLobe | color lpe:CD3[DS].*[<L.>O] |
color directSpecularPrimaryLobe | color lpe:CS2[<L.>O] |
color indirectSpecularPrimaryLobe | color lpe:CS2[DS].+[<L.>O] |
color directSpecularRoughLobe | color lpe:CS3[<L.>O] |
color indirectSpecularRoughLobe | color lpe:CS3[DS].+[<L.>O] |
color directSpecularClearcoatLobe | color lpe:CS4[<L.>O] |
color indirectSpecularClearcoatLobe | color lpe:CS4[DS].+[<L.>O] |
color directSpecularIridescenceLobe | color lpe:CS5[<L.>O] |
color indirectSpecularIridescenceLobe | color lpe:CS5[DS].+[<L.>O] |
color directSpecularFuzzLobe | color lpe:CS6[<L.>O] |
color indirectSpecularFuzzLobe | color lpe:CS6[DS].+[<L.>O] |
color transmissiveSingleScatterLobe | color lpe:CS7[DS].*[<L.>O] |
color directSpecularGlassLobe | color lpe:C<RS8>[<L.>O] |
color indirectSpecularGlassLobe | color lpe:C<RS8>[DS].+[<L.>O] |
color transmissiveGlassLobe | color lpe:C<TS8>[DS].*[<L.>O] |
color emissive | color lpe:C[<L.>O] |
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LPE Macro
If a custom LPE is useful for your shots, you can add your custom LPE by creating a macro in rendermn.ini file. The custom LPE will appear in the RenderMan for Maya (RfM) LPE list after relaunching Maya. For example:
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| Code Block |
|---|
Attribute "identifier" "string lpegroup" ["ground"] DisplayChannel "varying color plane2Shadow" "string source" ["color lpe:shadows;C<.[DS].'ground'><L.>"] |
Predefined LPE Groups
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- In the documentation examples we often use <L.> 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).
- Using . in place of DS is shorthand, if you are using a User Lobe, you must specify U and cannot use the . shorthand