GL_FRAMEBUFFER_SRGB and Srgba8 vs Rgba8 render target

[norru]

I'm working on my toy project, for which I'm using a simple HDR pipeline. All the rendering and postprocessing is linear and I'm using FP16 render targets, until the tonemapping step, when I resolve the framebuffer to Rgba8.

At some point I realized I was missing the gamma conversion step - so I added it to my tone mapping shader.

When I got unexpected results, I guessed it was because the graphics driver was doing the conversion for me automatically. Digging deeper, it turns out it didn't but I could turn the feature on by rendering to a Srgba8 framebuffer.

I got the same results as Rgba8. Doing some investigation, I found that in order for OpenGL backend to to do so, GL_FRAMEBUFFER_SRGB must be enabled (together with setting the render target's format to Srgba8).

GL_FRAMEBUFFER_SRGB doesn't turn out from any search in gfx-rs. Is this a bug?

[kvark]

It is enabled by default. Our examples are mostly gamma correct, last time I checked.
Here is a piece from src/backend/gl/lib.rs:

        if caps.srgb_color_supported {
            unsafe {
                gl.Enable(gl::FRAMEBUFFER_SRGB);
            }
        }

[norru]

Ok, I've missed that bit. Should I switch to Srgba8 then? At a first glance, it does not make any difference (but perhaps I need to check twice). I'm also assuming this doesn't apply to FP16 render targets.

[kvark]

Yes, that should do it.

On Jun 13, 2016, at 8:08, Nico Orrù [email protected] wrote:

Ok, I've missed that bit. Should I switch to Srgba8 then?

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[norru]

Thanks :)