Sign in to follow this  

Multitexturing with 3 Texture Units

This topic is 3341 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hello! Is it possible to blend 2 textures with an alpha-texture with a graphic card which has only 3 Texture Units? I would like to calculate: FinalColor = TexA*(AlphaTex) + TexB*(1-AlphaTex) Every solution I have ever seen used 4 Textures (2 normal textures and two alphas). Is there a way to do it with 3 textures? How do I have to configure the blending stages? Thanks for any advice!

Share this post


Link to post
Share on other sites
Hi,

I really recommend to use shaders for solution to this. Although it can be done with several texture units ... look closer here:

Link

The best solution would probably be using GL_INTERPOLATE_EXT token for glTexEnvi (or glTexEnvf, ...) - it does this - Arg0 * (Arg2) + Arg1 * (1-Arg2), e.g. exactly what you want.
Dunno if this is correct, but it should be written like (not sure, please anybody correct me if this is wrong ... I hadn't time to test it):

// first setup first texture unit
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, TexA);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, TexB);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_EXT)
glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB_EXT, GL_INTERPOLATE_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE0_RGB_EXT, GL_TEXTURE1);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB_EXT, GL_SRC_COLOR);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE1_RGB_EXT, GL_PREVIOUS_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB_EXT, GL_SRC_COLOR);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE2_RGB_EXT, GL_PRIMARY_COLOR_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND2_RGB_EXT, GL_SRC_COLOR);

glActiveTexture(GL_TEXTURE2);
glBindTexture(GL_TEXTURE_2D, AlphaTex);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB_EXT, GL_INTERPOLATE_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE0_RGB_EXT, GL_PREVIOUS_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB_EXT, GL_SRC_COLOR);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE1_RGB_EXT, GL_TEXTURE2);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB_EXT, GL_SRC_COLOR);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE2_RGB_EXT, GL_PRIMARY_COLOR_EXT);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND2_RGB_EXT, GL_SRC_COLOR);

Share this post


Link to post
Share on other sites
Thanks for your answer - will try it later on!

Unfortunately, my graphic card has not only not more than 3 TU but also no support for Shaders :-) It's an old ATI Mobility Radeon.

Share this post


Link to post
Share on other sites

This topic is 3341 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this