Improved Area Lighting in WebGL & ThreeJS

Question

I have been working on an area lighting implementation in WebGL similar to this demo:

http://threejs.org/examples/webgldeferred_arealights.html

The above imp

Answer 1

Hm. Odd question! It seems like you started out with a very specific approximation and are now working your way backward to the right solution.

If we stick to only diffuse and a surface that is flat (has only one normal) what is the incoming diffuse light? Even if we stick to every incoming light has a direction and intensity, and we just take allin = integral(lightin) ((lightin).(normal))*light this is hard. so the whole problem is solving this integral. with point light you cheat by making it a sum and pulling the light out. That works fine for point lights without shadows etc. now what you really want to do is to solve that integral. that's what you can do with some kind of light probes, spherical harmonics or many other techniques. or some tricks to estimate the amount of light from a rectangle.

For me it always helps to think of the hemisphere above the point you want to light. You need all of the light coming in. Some is less important, some more. That's what your normal is for. In a production raytracer you could just sample a few thousand points and have a good guess. In realtime you have to guess a lot faster. And that's what your library code does: A quick choice for a good (but flawed) guess.

And that's where I think you are going backwards: You realized that they are making a guess, and that it sucks sometimes (that's the nature of guessing). Now, don't try to fix their guess, but come up with a better one! And maybe try to understand why they picked that guess. A good approximation is not about being good at corner cases but at degrading well. That's what this one looks like to me. (Again, sorry, I'm to lazy to read the three.js code now).

So to answer your question:

• I think you are going about it the wrong way. You are starting with a highly optimized idea, and are trying to fix that. Better to start from the problem.
• Solve one thing at a time. Your screenshot has a lot of specular, that is unrelated to your problem but very visual and was probably a big influence to the people designing the model.
• You are on the right track and have a much better idea about rendering than most people. That can work for and against you. Read up on some modern game engines and their lighting models. You will always find a fascinating combination of hacks and deep understanding. The deep understanding is what drives picking the right hacks :)

Hope this helps. I might be totally wrong here and rambling at somebody who is just looking for some quick math, in that case I apologize.