1) change shader system: look into fx files
2) tone mapping
   bloom (gaussian blur)
   use downsampling: first 4x4 to luminance then 3 times further to 1x1
   use 3 new render render targets for this

3) mrt channels:

2 mrts:

mrt 1: rgba color + emmissive / luminance
mrt 2: world pos + projected depth
mrt 3: normals + w coordinate
mrt 4: flip-flop for mrt1


4) idea: donwsample color texture for ao

5) use depth formula on projected depth (or use linear depth)
   in order to combine ao + diffuse lookup into on texture lookup


reorder mrts:

mrt 1: rgba color + projected depth
mrt 2: luminance
mrt 3: normals + w coordinate
mrt 4: flip-flop with mrt1 / store luminance after ssao


6) render sun disc