Gamma correction in OpenGL

Triad_prague · 2011-10-23T10:03:36

I just realized that some games provide the user with the capability to set the "brightness" or gamma correction (CMIIW). I want to implement it but I wonder how would I go for it in OpenGL? Do you know if such a way exist? Thanks before

Graphics and GPU Programming Programming OpenGL

Started by Triad_prague October 21, 2011 09:20 AM

11 comments, last by Triad_prague 12 years, 5 months ago

samoth

9,833

October 21, 2011 06:02 PM

Maybe I'm not getting this right, but isn't proper gamma correction in OpenGL as much as using the *_SRGB constant for defining textures (to convert to linear space), and creating a SRGB framebuffer (to convert back)?

This is something I understand runs completely in hardware nowadays without any special tweaks needed (and, also in absence of shaders).

V-man

813

October 22, 2011 03:25 AM

Old games (
of course I'm talking about Windows), use http://msdn.microsoft.com/en-us/library/dd372194%28VS.85%29.aspx

Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);

L. Spiro

25,818

October 22, 2011 03:49 AM

Gamma correction is a non-linear operation, so I doubt that you can do it with additive or subtractive blending or even another blending.

However, I'd say that gamma correction shouldn't be looked at in OpenGL at all. IMHO it is part of the windowing system or monitor device settings.

This article explains why you should perform your color blending in linear space.
I updated my engine to use linear lighting and it really made a difference. The colors are much more realistic now.

L. Spiro

I restore Nintendo 64 video-game OST’s into HD! https://www.youtube.com/channel/UCCtX_wedtZ5BoyQBXEhnVZw/playlists?view=1&sort=lad&flow=grid