texture combiners

Yes, it is possible. How exactly depends on the type of texture combiners you are using.

But seriously, just use shaders. Texture combiners are so obsolete and inflexible, it isn't even funny anymore. Doing what you want is a five second job when using a shader.

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Original post by Yann L Yes, it is possible. How exactly depends on the type of texture combiners you are using. But seriously, just use shaders. Texture combiners are so obsolete and inflexible, it isn't even funny anymore. Doing what you want is a five second job when using a shader.

I agree .. using shaders this is a piece of cake... but I have people asking me how to do this with OpenGL and using the multitextering combiners...

if this is possible.. then how? remember I have no alpha in my textures... I have don't this succesful with textures with alpha.. but I would like to see if I can do the same without alpha.

Direct3D actually has something that allows you to use alpha on the RGB components... but how is this done in OpenGL.

Peter

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Original post by Crisium Direct3D actually has something that allows you to use alpha on the RGB components... but how is this done in OpenGL.

As I said, it depends on the type of combiners you are using. You didn't specify this.

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Original post by Crisium but I have people asking me how to do this with OpenGL and using the multitextering combiners...

If you don't mind me asking, why would anyone want to do something like this ? I mean, all 3D cards of the few last generations will internally emulate combiners with shaders anyway. So it doesn't make any sense not to use shaders directly.

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Original post by Yann L Quote: Original post by Crisium Direct3D actually has something that allows you to use alpha on the RGB components... but how is this done in OpenGL. As I said, it depends on the type of combiners you are using. You didn't specify this. Quote: Original post by Crisium but I have people asking me how to do this with OpenGL and using the multitextering combiners... If you don't mind me asking, why would anyone want to do something like this ? I mean, all 3D cards of the few last generations will internally emulate combiners with shaders anyway. So it doesn't make any sense not to use shaders directly.

I'm using glTexEnvi.

Some people still use older version of OpenGL and graphics cards for reasons I do not need to know.

Peter

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Original post by Crisium I'm using glTexEnvi.

Of course you do, all types of combiners use glTexEnv. You need to specify the exact type of combiner you use (texture_env_combine, register combiners, etc)

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Original post by Yann L Quote: Original post by Crisium I'm using glTexEnvi. Of course you do, all types of combiners use glTexEnv. You need to specify the exact type of combiner you use (texture_env_combine, register combiners, etc)

glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_ARB);

Peter

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Original post by Crisium glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_ARB);

You still don't specify if you are using ARB_texture_env_combine or EXT_texture_env_combine. In the future, please be more precise in your questions. This will save us the guessing around. For now, I'll assume the former.

This a very primitive combiner extension, and so your options are limited. You cannot get the alpha from a colour source. But you can use a colour source to interpolate between two textures. So use combiner mode INTERPOLATE, Arg0 is your first textures' colour, Arg1 your second texture colour, and Arg2 again your first texture colour.

Note that this will only work if the text in the first texture is guaranteed to only contain shades of grey. If it contains other colours, then the blending will be pretty strange, since you don't do any RGB to greyscale conversion for the interpolation factor.

Also, this will only work with ARB_texture_env_combine, and NOT with EXT_texture_env_combine. The latter doesn't allow colour sources for Arg2.

Just out of curiosity, how would this be done with a shader (GLSL or Cg)?

Sounds like just doing a modulation would work.
With standard GL,
glActiveTexture(GL_TEXTURE0);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glActiveTexture(GL_TEXTURE1);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

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Just out of curiosity, how would this be done with a shader (GLSL or Cg)?

How complicated is it to sampler a couple of a texture?

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Original post by V-man Sounds like just doing a modulation would work. With standard GL, glActiveTexture(GL_TEXTURE0); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glActiveTexture(GL_TEXTURE1); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); Quote: Just out of curiosity, how would this be done with a shader (GLSL or Cg)? How complicated is it to sampler a couple of a texture?

modulate two times? does that make sense at all?
modulate is how it should combine the textures, so one modulate is
all you are going to be able to use (as I understand it)

so I don't think your sample will work at all to my orginal question.

Peter

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Original post by Yann L Quote: Original post by Crisium glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_ARB); You still don't specify if you are using ARB_texture_env_combine or EXT_texture_env_combine. In the future, please be more precise in your questions. This will save us the guessing around. For now, I'll assume the former. This a very primitive combiner extension, and so your options are limited. You cannot get the alpha from a colour source. But you can use a colour source to interpolate between two textures. So use combiner mode INTERPOLATE, Arg0 is your first textures' colour, Arg1 your second texture colour, and Arg2 again your first texture colour. Note that this will only work if the text in the first texture is guaranteed to only contain shades of grey. If it contains other colours, then the blending will be pretty strange, since you don't do any RGB to greyscale conversion for the interpolation factor. Also, this will only work with ARB_texture_env_combine, and NOT with EXT_texture_env_combine. The latter doesn't allow colour sources for Arg2.

sorry, but yes ARB_texture_env_combine is the right one.
I will try your suggestion later today. but just looking at it I can't really see how it will mask the black areas around the text out. logically I would think it would have to use the RGB as alpha from the first texture. ... but let me try your example and I'll have an answer.

thanks for your suggestion,
Peter

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Original post by Crisium Quote: Original post by V-man Sounds like just doing a modulation would work. With standard GL, glActiveTexture(GL_TEXTURE0); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glActiveTexture(GL_TEXTURE1); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); Quote: Just out of curiosity, how would this be done with a shader (GLSL or Cg)? How complicated is it to sampler a couple of a texture? modulate two times? does that make sense at all? modulate is how it should combine the textures, so one modulate is all you are going to be able to use (as I understand it) so I don't think your sample will work at all to my orginal question. Peter

Well, you have to setup stage 0 and stage 1 texture unit. If you want, try
glActiveTexture(GL_TEXTURE0);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glActiveTexture(GL_TEXTURE1);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

That will just take tex0 and modulate with tex1.
When you use modulate on tex unit0, it modulates with the primary color.