Motion Graphics by Jeremy Clark

Posts tagged “global illumination

More Indirect Lighting In Maya – Caustics

Within my Film Noir Inspired Lounge scene I also set about learning how to render “Caustics” in Maya and Mental Ray.

“Caustic lighting” generally refers to the patterns of light that are formed when rays of light pass through a transparent material, and are refracted  in a way that patterns appear projected onto surrounding objects. Think of shining a light through a glass of water, and seeing the patterns of light that are produced on the table.

Within Maya, “Caustics” are considered a form of Indirect lighting, as they rely on the use of Global Illumination Photons. For this reason, the workflow for including Caustics in a scene is similar to that of enabling Global Illumination within a render.

Though somewhat straighforward to enable, caustics can be tricky to fine tune, and there are a number of variables that dictate their appearance and quality in a render. Here’s how I implimented them within my scene:

1.) Just like when setting up my Global Illumination lighting, I wanted to keep my Caustic Photon emmitting lights separate from my scene lights. For each light that I wished to appear as if casting the Caustics, I duplicated the light, dropped the cloned light’s “Intensity” to zero, and enabled “Emit Photons” under the new lights “Mental Ray –> Global Illumination and Caustics” attribute editor tab.

2.) Next I jumped into Maya’s “Render Sttings” tab and under the “Indirect Light” tab, I opened the”Caustics” tab and clicked to enable them.

3.) Now came the hard part – fine tuning them to achive a decent enough look. Key settings I tweaked included:

– From the Caustic Light’s shape node Attributes Editor  –> “Mental Ray” –> “Caustic and Global Illumination” dropdown: Photon Intensity (A lower than default value worked well here), “Caustic Photons” (I increaded the number of Photons by 10x the default here), and “Exponent” (I decreased the value from 2.0 to 1.5 here to increase the brightnes of my Caustics patterning.

– Under the “Render Settings” –>”Indirect Lighting” –> “Caustics” tab I set to lower the accuracy from 100 (Default) down to 40. Apparently decreasing the value here is better.

The following depicts two renders of the same lamp, one without , and one with Caustics enabled. Note the patterns formed by the light on the wall behind the glass of the lamp.

This shows a render of one of the lamps in my scene without Caustics enabled.

.. And this is the same lamp, rendered again but with Caustics eneabled.

Though in this scene the effects of Caustics appear somewhat minimal, I still wished to learn about how to use them for a greater understanding of how Indirect lighting works in Maya.

Global Illumination In Maya

My Introduction to Indirect Lighting

Continuing with my Survival-Horror inspired scene in Maya, I’ve started experimenting with different lighting techniques. Having up until this point only utilized simple direct lighting setups to light my scenes, I’ve now moved on to learn more about how to use “Indirect Lighting” to improve the look of my renders.

“Indirect Lighting” occurs when light that is emitted from a direct source (A “Light” in Maya, for example) bounces off of surfaces in the scene. It is from this behavior that this kind of light can also be referred to as “Secondary Light”.

When the light contacts a surface it can take colour from this surface along with it. This newly coloured “secondary” light then lights other objects in our scene.

Global Illumination

The first type of Indirect Lighting that I’ve started to play with in Maya is known as “Global Illumination”. Here light sources are created, and set to “Emit Photons”. These “Photons” travel from the light source and bounce around our scene just like light does in the real world.

It seems that Global Illumination works best if you separate the Direct and Indirect light sources within a scence. Leave the “Direct” lights to provide basic light on objects and cast the scene’s shadows,  and create seperate lights that will emit the Photons required for our Global Illumination.

Therefore we select our “Secondary Light” sources, set their standard “Intensity” to zero (So they do not cast any direct light), but enable “Emit Photons” instead.

Here are two renders of the same scene – one with Global Illumination enabled and one without.

Render withough Global Illumination - Relying only on direct scene lighting.

Render with Global Illumination enabled