Photon RTXPT
Lights
Area, sun, dome, and mesh lights in physical units.
Every Photon Light works in physical units — lumens for emitters, lux for the sun, EV-relative intensity everywhere. Match a lighting plot's numbers and the render agrees with the venue.
Light types
| Type | Shape | Intensity unit | Shadows |
|---|---|---|---|
| Area | rect / disc / sphere | lumens | soft, size-driven |
| Sun | directional | lux | sharp, angular-diameter |
| Dome | HDRI environment | EV offset | image-based |
| Mesh | any SOP | nits | from geometry |
Driving lights live
Light parameters accept CHOP exports without resetting accumulation — they're part of the light-sampling pass, not the scene build.
# sACN in a CHOP, mapped straight onto a light
op('photonlight_key').par.intensity.expr = "op('sacn1')['u1c1'] * 15000"Dome + area is the standard stage recipe: dome at −2 EV for ambience, area lights carrying the key. Start there before adding mesh emitters — they are the most expensive type to sample.
A mesh light with thousands of triangles samples poorly and shows as noise in shadows. Decimate emitter geometry to the silhouette — the light looks identical and converges far faster.