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| LPE Events | Description | Example |
|---|---|---|
C | Camera | |
<type event 'group'> | Scattering event specified by scattering type, scattering event, or lpe group | C<.[DS]'floor'>[LO] matches all light paths 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 event | <.D> where the period represents R or T |
| Scattering Types | ||
R | Reflection | C<R[DS]>[DS]*[LO] matches all reflected light paths |
T | Transmission or refraction | C<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 events | CDSL, C(DS)L, and CD(SL) are all functionally the same |
| Alternatives | ||
| | | A vertical bar separates alternatives | CD|(SD)L matches direct diffuse or specular-diffuse light paths |
| [ ] | Square brackets that match any one of the enclosed events | C[D2D3]L matches direct diffuse2 or diffuse3 light paths |
[^ ] | 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 |
{n} | Curly brackets that match the preceding event exactly n times | C<T[DS]>{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]{0,1}[LO] matches direct and emissive light paths |
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