doh, sorry, I thought you said lighting. I don't sleep much, my mistake. If you have photoshop with the xenofx plug in, that's what I use anytime I want lightning. Here's one idea I haven't tried, but it should work. Take a bare tree model boolean it until you have only the branchings you want, turn it upside down, apply a texture that would make it appear to be light, then take the render into photoshop, select the lightning by using the wand, then apply eye candy's glow filter to it. Sorry about the misunderstanding.

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