do luminance texture's still exist to openGL?,
Crossbones+ - Reputation: 6158
Posted 24 November 2012 - 05:08 PM
their's a single mention of luminance in the 3D pages, which isn't helpful.
so, in short, if it's not in the docs, should i ignore the type(i've used it in the past, and am faily certain it was in older documentation.)?
or are the docs just incomplete?
Moderators - Reputation: 9968
Posted 24 November 2012 - 05:42 PM
The old names implied a usage (GL_ALPHA for an alpha texture, for example) and there were multiple formats with a single color channel, but had different behavior when it came to what four channel color value was returned from sampling a one or two channel format. For example, a luminance value of L returned the RGBA value (L, L, L, 1), while an intensity value I returned the RGBA value (I, I, I, I). It made a difference for the fixed functions which were not programmable and you had to select the precise format such that, for example, the alpha channel became correct. Now when we have fully programmable shaders, it makes sense to disconnect the name of the format with the actual usage which is entirely arbitrary within your shader.
Now you effectively only specify how many color channels you want with GL_RED, GL_RG, GL_RGB and GL_RGBA, and, of course, variants thereof to narrow in on exact channel format and precision.