regarding the downsampling:
I'm not really sure... I'm using 13 samples per pixel for the first downsample step (to prevent ugly
aliasing) and for the other downsample passes I use less samples because it's already blurred then.
When upsampling you have to be careful about the resolutions. if for example:
screen_size.y (1080) / 16 = 67.5 -> you have to compensate the difference that the .5 causes.
EDIT: didn't see that you want to downsample to 1x1
What I did: render the average of multiple samples into a 1x1 texture. I'm pretty sure most games do something similar.
About gamma correction: I'm not doing any gamma-correction (I'm not sure if it's THAT important),
however gamma correct lighting is important.
I want to do high dynamic range rendering. Does this just mean to do every the same as always,
but instead of rendering into RGB888 targets, I will render into floating point render targets?
Well... yes thats all you need to make HDRR possible.
However, I use bloom (and a little color modification) to illustrate colors which are out of range,
my tonemapping just adds some sharpness.
It looks like this at the moment:
(the bright spots are ~30 times brighter than the maximum)