Multitexture without blending

OpenGL OpenGL: Advanced Coding
1

Hi.

I have a question to You, I have thought that You will be able me to help, if You not against.
I use GL_ARB_multitexture for imposition of the second texture on polygon.
This works well, but only for lightmaps.

I want to hear possible with use GL_ARB_mutlitexture:

  1. Do the second texture not blending and possible control this blending?

  2. Possible impose on polygon environment texture, as the second texture
    and do her blending or on the contrary?

I have advised to use GL_EXT_texture_env_combine.
I tried to use this extension, but I have not got the due result.

Please if You know as this do, help me, if possible that show this
in the manner of source code.

Sorry for my English.

2

What is the point of using multitexture and NOT blending the two textures? If the second texture just replaces the first, why would you use the first at all?

I’ll assume that this isn’t really what you meant to ask, so can you explain precisely what it is you’re hoping to achieve?

– Tom

3

Example:

One texture with alpha channel (transparent)
Second texture with no blending

or

One texture with alpha channel (transparent)
Second texture with blending
Third texture with env mapping no blending

Sorry if You not understand

4

I think you do not understand what blending is. I suggest you get some documentation about it.

Basically blending enables you to “mix” two colors (textures) according to a blending function (add, subtract, multiply, …).

If your application does not need to mix two textures, then you do not need blending but you do not need multitexture either.

I must say I did not understand your examples: can you explain them more precisely ?

Regards.

Eric

5

If you can, please run Quake III Arena
and start level q3dm10. See on env effects on walls.

How me do this with multitexture extensions like ARB.

Good examples, i think.

6

Use glTexEnv*() to configure the way multiple textures are combined. Here’s a list of possible operations from the GL_ARB_texture_env_combine spec (which you should read carefully):

REPLACE                 Arg0
MODULATE                Arg0 * Arg1
ADD                     Arg0 + Arg1
ADD_SIGNED_ARB          Arg0 + Arg1 - 0.5
SUBTRACT_ARB            Arg0 - Arg1
INTERPOLATE_ARB         Arg0 * (Arg2) + Arg1 * (1-Arg2)

For environment maps, you’ll want GL_ADD.

– Tom

7

Very big thanks.

8

I’m also interested about this topic and would like know also how to controll blending with multitextures?