View Full Version : Physically Correct Lights? sthing I found in document

04 April 2007, 03:40 AM
Well, must say in 8.5, the maya document is better a lot.
I am digging the mia_material document and found this

Use Physically Correct Lights

When GI is enabled, light sources shoot photons. It is imperative for the mia_material (or any other mental ray material) to work properly for the energy of these photons to match the direct light cast by that same light! And since photons model light in a physical manner, decay is "built in".

Hence, when using GI:

Light sources must be emitting photons at the correct energy
The direct light must decay in a physically correct way to match the decay of the photons.
Therefore it is important to make sure the light shader and the photon emission shader of the lights work well together.

So, I could plug a physical light shader into light shader to get a real decay light, but what is a photon emission shader for light? I found none of them in MR material...

Some definition found in

Photon Emission Shader

Photons are emitted from the IBL environment sphere. These photons pick up their energies (or colors) from the IBL texture. A photon emission shader emits all its photons once per frame. It is more active than an environment shader in this sense. Photons work best with mostly diffuse IBL textures.

But can not find a shader for testing right now :(

04 April 2007, 09:37 AM
The photon emission shader is built into the maya light, it's basically everything in the 'Caustic and Global Illumination' tab of the light, so you dont have to care about that. The value of the physical light's color should go into the Photon Intensity to have 'matching decay'.

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04 April 2007, 09:37 AM
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