cobaltdream,

Me: I think a "null" object is one you put in the scene for parenting purposes or for indicating important points for use in math, but it doesn't actually render anything.

You: i don't think that's what they meant in that tutorial. it seemed to have something to do with lighting.

Tut: The GI effect in this scene is achieved mainly with gradients ***based on distance of Null objects: 
***I don't understand your point. I said "or for indicating important points for use in math" which is exactly what the fake GI shader in the article is doing. It uses math to compute the distance to the Null objects to decide how to shade the walls to SIMULATE lighting. So yes it has something to do with "lighting" but not real lighting - rather simulating lighting and shadow in a shader - which is the point of this thread.

The technique does not require NULL objects. You could type coordinates into the shader and you would not need NULL objects at all. The convenience of the NULL objects is because you have a 3D preview that lets you move them where you want them in the scene, and not have to bother with guessing the coordinates at all, and these coordinates are needed to implement the gradient in the shader mathematically in such a way that reacts to the position of the interesting point - the origin of the faked light..

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)