PDA

View Full Version : GL_DOT3_RGB_ARB and GL_COMBINE_ALPHA_ARB



Hampel
12-17-2002, 09:36 AM
The extension specification for GL_ARB_TEXTURE_ENV_DOT3 (http://oss.sgi.com/projects/ogl-sample/registry/ARB/texture_env_dot3.txt) states that GL_DOT3_RGB(A)_ARB can be used together with GL_COMBINE_ALPHA_ARB. The following table, however, contains only the case for GL_COMBINE_RGB_ARB.

Now to my point: is it possible to use GL_DOT3_RGB_ARB together with GL_COMBINE_ALPHA_ARB to calculate only an alpha value and to use GL_COMBINE_RGB_ARB with another texturing function (e.g. GL_INTERPOLATE_ARB) to calculate the RGB values simultaniously?

ScottManDeath
12-18-2002, 03:40 AM
Hi

thats not possible. You can use DOT3_RGB as the COMBINE_RGB function and any other (not DOT3_RGB(A) ) as the alpha combiner function. If you use Dot3_RGBA, the dotproduct gets copied into alpha and the COMBINE_ALPHA function is ignored.

Bye
ScottManDeath