Moving to full HDR?

[klepto2]

As posted on discord I have tried to improve the existing Bloom shader to go more to the current industry standard. While the bloom shader is good and solid, its technique is a bit outdated and normally not used anymore.  Also a lot of posteprocessing effects, overall lighting in PBR reflections, etc might look better when switching to a full HDR pipeline.

Current state (from my investigations):

• The framebuffer uses RGBA8 format
• This framebuffer is passed to the posteffect pipeline as an "entry" texture
  • So no posteffect can use real HDR operation

Proposed state:

• The framebuffer should use GL_R11F_G11F_B10F or GL_RGBA16F
• With this colors can be  stored in their HDR form 
• Before displaying a tonemapping should be applied 

Why:

Lets take a closer look to Bloom (I have just focused on it, but can provide more samples if wanted)

Lets say you have a very green object with a Color RGB = 80,255,74 or in Vec4 it would be (0.31,1.0, 0.29).
SDR: 

• When adding lighting etc. to it or change the brightness to something above lets say 400
  • The resulting color in the rendering will always be 1.0,1.0,1.0 
  • It is clamped by the RGBA8 format 
  • Adding thinks like tonemapping, reflections etc will look washed out :
    

HDR:

• Same as for LDR 
  • Without any lighting the stored color will now be vec3: 1.24, 4.0, 1.16
  • this can properly be used for bloom to define where bloom will occur
    • with the current approach white areas (1.0,1.0,1.0) are considered blooming even if they shouldn't
    • with hdr those pure white areas stay uneffected and only real emitting surfaces are providing bloom.
    • not only that, the bloom will be more physically correct: like in this sample:
    • you can see that in the middle: the emmision accumulates up in the middle and the emission fades out with the distance.

Some more resources: 

• https://www.youtube.com/watch?v=tI70-HIc5ro
• https://www.iryoku.com/next-generation-post-processing-in-call-of-duty-advanced-warfare/
•  

[Josh]

If you are rendering to a texture, as you are when any post-processing or MSAA is in use, the color format is RGBA16F. So as you are performing rendering, all the intermediate steps will use high=precision color, and the results don't get clamped to 0-1 until the final output.

I don't have an HDR monitor, so I don't currently have any way of testing HDR color output.

I am sending some code for the framebuffer setup you can experiment with if you would like.