I am studying about blender game engine.
In these days, i focus on texture baking in blender internal render-er for high quality game 
I have a question for difference Internal and Cycles render engine.
First, please see picture below.
You can see shadow area is very different. Dim light of Internal Render-or’s is not focused.
Can make focused (dim) light of transparency object in Blender Internal Render-or?
The term you’re looking for to describe this is “caustics”. Knowing that much, I did a quick search. Hopefully this is what you need:
You can “fake” it using Blender Internal. In this situation I turned on Indirect Lighting.(isn’t that what caustics are?) I set the Emit for the sphere to 0.01. (very low). Then I turned up the Indirect Lighting Factor to 100 (very high). I set the Indirect Lighting drop off fairly sharp with a value of 4. This keeps the glow near the emitting object. One bounce for Indirect Lighting is all you need. In this setup, the shadow color is still completely separate and adjustable from the red glow.
The fake is the method of Indirect Lighting. It can only produce circular patterns on a target surface. Thus the pointed GEM object suffers the most. Cycles gets it right in the shape of the caustic. BI is just a soft glow.
269_fake_caustic.blend (110 KB)
