Light shader tip

Written by Jeff Patton on 21 September 2007.

If you've ever been frustrated that the mr Area Omni & mr Area Spot lights emit light as though they are point lights, this tip is for you. If you don't know what I'm talking about, hopefully the following info will help explain it.

Example: If you add a mr Area Omni light to your scene and then set the type to Cylinder in the Area Light Parameters roll-out of the light. Then set the height to something rather large like 60" or more and of course you'll need to enable the 'Show Icon in Renderer' option to see this...now render.

You'll get a result like this (click to enlarge)


Notice how the light is emitted from the center of the cylinder instead of along the entire length of the cylinder shape? That's the problem that I'm referring to.

Now, if you assign a light shader to the mr Area Omni, it will emit light evenly along the entire length of the cylinder:

After assigning a light shader (click to enlarge)


Words of caution:
Keep in mind that when you assign a light shader, it affects how photons are emitted. So this method probably isn't a great idea for scenes where you use GI or Caustics...but for FG only scenes it can be useful.

Also, generally speaking you should normally use photometric lights in your scenes instead of the standard lights or the two mental ray area light types. YES, photometric lights work with mental ray and provide the most realistic results, provided your scene is modeled to a proper scale.

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