Motion Graphics by Jeremy Clark

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

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5 responses

  1. Max

    Yep, light is hard 😦

    I’m only using the most basic of light at present.

    I used a yellow spotlight. It was casting too much shadow, and was making the scene more yellow than I had intended, so I simply put another spotlight at the same posistion, but made it white, and set it to cast no shadows. This reduced the harshness of the end shadow, and lowered the yellow a little.

    One day I’ll learn to do it the proper way 🙂

    February 24, 2012 at 5:33 am

    • Wow yeah, tell me about it. I’ve been attempting to use Caustics with transparent surfaces too – It’s certainly tricky to get it right!

      My “to learn” list is always growing when it comes to this stuff. Are you mainly working in Maya or Blender these days may I ask?

      February 26, 2012 at 11:48 pm

  2. Max

    Mainly working… i’m actually being pretty slack, just started back at 3D last month, first time since the course.

    I am just using blender at present. All i’ve done (most simpliest of stuff) is on my blog, i’m way way way (liek a year or so) behind your level.

    February 27, 2012 at 12:49 am

  3. There’s an another technique 😉 If you use Final Gather in combo with GI, you can render the scene even without lights! (meaning, the objects with high incandescence acts like light sources). you can use lights just for the sake of rendering shadows or even you can apply the shadow layer separate in post-processing. It’s very technical but once mastered, it produces awesome outputs. Oh, while using Caustics try to use Spotlight and keep the come angle acute! it will work! Good luck! 🙂

    March 15, 2012 at 11:11 am

    • Hi! Thanks very much for the advice regarding caustics and indirect lighting. I’ll try out the techniques you mentioned and perhaps upload some renders soon 🙂

      March 19, 2012 at 7:56 am

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