Maya 6 Mental Ray
Compiled tables of Global Illumination,
Final Gathering, and Photon Intensity

This obviously dated page (circa 2004) continues to garner hits and so lingers on.

What is the relationship between normal light illumination, global illumination (GI), final gathering (FG), and photon intensity? The tables below attempts to answer that question for a fixed illumination intensity (1000 with quadratic falloff). The first table demonstrates photons only scenes with no specular/diffuse lighting turned off, while the second table turns on lighting.

On the surface, it seems that FG is linked to photon intensity only when both FG and GI are on. Note, when FG (and the light) is on, it predominates. Thus suggests workflow should start with FG only, tune slightly dark, then turn on GI to soften the areas in darkness. This is exacly what everyone does. Well, draw your own conclusions.

Note: Maya standard shaders only - no DGS material and DGS photon shaders used.

Photon Intensity
Table 1: Light (diffuse/specular) off, photons only
GI on
FG on
GI on
FG off
GI off
FG on
0 (emitt off) Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
4000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
8000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
16000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
32000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
64000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
128000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image

 

Photon Intensity Table 2: Light (diffuse/specular) on with photons
GI on
FG on
GI on
FG off
GI off
FG on
GI off
FG off
0 (emitt off) Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
4000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
8000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
16000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
32000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
64000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image
128000 Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image Maya 6 FI, GI, Photon Illumination Image

Scene Description

nurbs sphere, scale 2
lambert (.8, 0, 0) red
polygon cube, scale 10, front face missing
lambert (.8, .8, 0) yellow

point light, translate 20 in X, quadradic, intensity 900, ray traced shadow, default 10000 globillums

mental ray, ray trace on

camera enviornment background color 50% gray (0.5, 0.5, 0.5)

Final gather rays reduced from 1000 to 300 to shorten rendering times

Global Illumination uses defaults

Maya 6.01