If someone could point me in the right direction that would be great. Like a great book or online reference.
I also still have problems with final output as you can see. I will fix this :-) Here's the shader.
varying vec4 vColor;
varying vec2 vTexCoord;
uniform sampler2D tex_d;
uniform sampler2D tex_n;
float exposure = 1.0;
oColour = texture2D( tex_d, vTexCoord);
oColour = 1.0 - exp2( -oColour * exposure );
gl_FragColor = oColour;
gl_FragColor.a = 1.0;