The glorious Godrays - shaders in Unity

 [http://s8.postimg.org/7e8xjn9gl/rays002.jpg]

When I first began to think about programming as a life choice waaay back, the thought of writing graphics code was not one that sprang to my mind. My idea of interesting, fun-to-write code was AI programming, and that's the kind of work I wanted to do. Now, I still do love me some AI (my latest blog posts about Alien AI and GOAP are dead giveaways) but I never imagined that my second best interest would be in shaders and graphics.

I usually detest the the Games Industry's blind obsession with graphical fidelity so prefect you'll weep tears of joy. But once I started learning GLSL and the visual effects you can achieve with it, I was hooked. I did toon-shading, bump mapping, dynamic lighting and shadowcasting. And now, since I am in the process of making a game involving God, I'm writing a Godray shader.

Godrays, or the official term Crepscular Rays, refers to shafts of light that appear to radiate from aingle point, usually behind an obstacle like clouds or a person. The light rays often darken the obstacle hiding the light source, and as a result it appears as though a bright glow is emanating from it.

 Neat little online demo of the effect in action






After a bit of research, I've managed to get a good idea of how you would simulate this effect in a shader. Simply render an occlusion map onto an FBO, render the lighting as normal, then overlay the occlusion onto it with blending to match the brightnesses of each. Overall this isn't that complex a concept, and if I were to write this in GLSL within an openGL framework it would be done in minutes. However, there are a few potential roadblocks:

1. Unity

I'm not sure how Unity will handle specific lighting effect shaders, especially if each lit object has to perform its own separate godray effect. I may have to manually add a light source behind major areas, and if so that will get annoying fast.

2. Unity

Unity uses its own shader language called ShaderLab. Why they didnt just use openGL, directX or even CG is beyond me. Espscially since most ShaderLab shaders use tunnelling to access the underlying CG code anyway. I dont think it'll pose too much of an issue, but it's still possible that ShaderLab will try and trip me up every 20 seconds.

3. Unity

Unity's system of materials, lighting and shaders is confusing. There are no ways to easily edit shader values and settings, and barely any notion of texture maps. According to the online Unity manual, there is a function concerned with render textures. But knowing Unity it won't be entirely code-handled, which means placing template materials in the scene, which means linking issues, which means...

Basically, I don't enjoy using Unity.