Re: [Yafray-devel] Producing HDR images with yafray

[Emmanuel Mogenet]

Diego Pino Navarro wrote:

> Hi,
>
> I don´t agree with you, i.e DV compression is so bad (YUV: 4:1:1) that 
> even your best color range gets messed up, 32 bit is only usefull for 
> Cine compositing(35mm, super 16 and maybe HD(10bits only) and depth 
> maps. but anyway


First, not all video is DV.
There aren't many video professionals I know  that work
with DV unless they've fallen down on hard times.

Second, the limitations of the final output format are irrelevant
to the discussion : when you are using elements generated by a
3D renderer in order to assemble a composite you are potentially
feeding your elements to a varying number of color correction passes,
convolutions, fake motion-blur and other 2D post-processing operations
that are either downright impossible or way to expensive to perform inside
the 3D renderer. At that point, if you do not have the full dynamic 
range that
was available inside the renderer, you are basically making your life 
very complicated.

Case in point : download the EXR library, and use the tree image example.

Now try the following:

      1. Downconvert the frame to 8bit
        . Apply a x5 brightness to light up the part that's in front of 
the tree
        . Shoot to video

      2. Apply the x5 brightness on the half-float EXR image
        . Downconvert the result to 8bit
        . Shoot to video

Compare the results.
You'll see that output of case 1 is as crappy as can be, whereas
the output of case 2 is clean, even though both are shot to video.

Other case in point : try to reproduce a half decent spotlight bloom effect
in a super-dark scene (like shooting car headlights at night) with an 8bit
pipeline. No way.

On the other hand, if you do it on a floating point pipeline and then shoot
to video, it'll look good, independent of the lame quality of the output 
media.

> I think you are not understanding opensource the right way, your idea 
> of posting code only to someone that can really help you is a little 
> selfish..but i can live with HDRI images as output, or modify teh 
> source(and post it) myself.

I'm not being selfish. If I was, I wouldn't offer to post the code. I 
just want
to make sure I'm sending my stuff someplace it serves an actual purpose.

> Documentation says you should avoid Gamma/Exposure correction, have 
> you tried it?

Nope, but I'll give it a shot.