Imagination PowerVR SDK Blog

Luminance alpha texture channel


#1

Hi,





I’m a Pandora (SGX530, OMAP3430) developer.





What channel/s is the luminance + alpha information mapped to in the fragment shader ? Is it RGBA = (L, 0, 0, A) ? Ideally i would want (L, L, L, A) since it means i wouldn’t need to convert my IA88 textures to RGBA8888 or create a seperate shader when ever i want to mix textures.





Is there any possibilty of the EXT_texture_swizzle extension making its way into the SGX drivers? I guess, at worst, it might add a few cycles to a shader but it might be worth it for some applications.


#2

http://www.khronos.org/opengles/sdk/docs/man/





GL_LUMINANCE_ALPHA


Each element is a luminance/alpha pair. The GL converts it to floating point, then assembles it into an RGBA element by replicating the luminance value three times for red, green, and blue. Each component is then clamped to the range [0,1].Tryum2010-07-06 09:24:26