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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<RD'floor'>[LO] matches diffuse reflections from the floor lpe group |
<L.'group'> | Light, i.e. analytic and geometric lights | C.*<L.'key'> matches all light paths from the key light group |
O | Emissive object, i.e. camera visible lights and material glow | C.*O matches all emissive object light paths |
| Wildcard | ||
. | A period will match any relevant scattering type or event | |
| Scattering Types | ||
R | Reflection | CR[LO] which is the same as C<R.>[LO] or C<R[DS]>[LO] matches direct reflection |
T | Transmission or refraction | CT[LO] which is the same as C<T.>[LO] or C<T[DS]>[LO] matches direct transmission |
| Scattering Events | ||
D | Diffuse lobes (D1, D2, D3, D4) | CD[LO] which is the same as C<.D>[LO] or C<[RT]D>[LO] matches direct diffuse. |
S | Specular/Glossy lobes (S1, S2, S3, S4, S5, S6, S7, S8) | CS[LO] which is the same as C<.S>[LO] or C<[RT]S>[LO] matches direct specular |
| User Event | ||
| User lobes 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 equivalent |
| Alternatives | ||
| | | A vertical bar separates alternatives | CD|(SD)L matches CDL or CSDL |
| [ ] | Square brackets that match any one of the enclosed events | C[S2 S3 S4S2S3S4]L matches 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) |
| Qualifiers | ||
* | An asterisk will match the preceding event zero or more times | C.*[LO] matches all light paths, including emissive |
+ | A plus sign will match the preceding event one or more times | C.+[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 | CT{2}[LO] matches double transmission light paths |
{min,} | Curly brackets that match the preceding event min or more times | C.{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.{0,2}[LO] matches all light paths with up to one bounce of indirect |
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