Light Pre-Pass Renderer

This week I decided to try and implement other interesting rendering thechniques, and after Googling a lot I've stumbled upon the Light Pre-Pass technique.
It's a very simple technique that consists in pre-calculating all the scene lighting.

So I have made my own version of it. Many implementations just re-calculate the fragment positions from depth, but I think that that is just too messy.

The idea is pretty straight-forward. It can be done in just three passes:

1.  Render the scene Normals and the Positions to a FBO.
• Optionally, you can store some material parameters in the alpha channels of the Normal  and Position maps like I did (Normal.a = Glossiness, Position.a = Specular Intensity).
• You can apply the normal and maybe the specular textures in this step.
2.  Into another FBO, render the lighting. This is where you calculate the light attenuation and the Lambert term for each light, based on the light properties from Pass 1.
• Here's where you bind the Normal and Position maps. Use them for the parameters for the light equation.
3.  Do a simple Forward rendering step and apply the lighting to the scene.
• Here you'll bind the resulting texture from Pass 2 and use gl_FragCoord.xy / ScreenRes as the texture coordinates since they're in screen space.
•  Also here is where you apply the diffuse textures.

Here is my GBuffer layout for the first pass:

	R	G	B	A
COLOR_ATTACHMENT0	Scene Normal			Material Glossiness
COLOR_ATTACHMENT1	Scene Position			Material Specular Intensity

And for the second pass:

	R	G	B	A
COLOR_ATTACHMENT0	Light Color (Lambert)			Specular (Phong)

This is the final result (Includes texturing and rim light):

That's it, until next time! 👍