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# OpenGL glActiveTexture does not switch texture unit

## 4 posts in this topic

Hi

I'm trying to pass 2 textures to fragment shader. But in shader only one texture is avaible.

I found that problem is in glActiveTexture.

After call with any args, like  glActiveTexture(GL_TEXTURE1), glActiveTexture(GL_TEXTURE2) .... i alway end in texture unit 0

here is part of code:

glActiveTexture(GL_TEXTURE0);

// debug
GLenum e = glGetError(); // e = 0
GLint nn;
glGetIntegerv(GL_ACTIVE_TEXTURE, &nn); // nn = GL_ACTIVE_TEXTURE = GL_TEXTURE0

glBindTexture(GL_TEXTURE_2D, leftEyeTextureHandle);

glActiveTexture(GL_TEXTURE1); // !!! <- it does not work

//debug
GLenum e = glGetError(); // e = 0
GLint nn;
glGetIntegerv(GL_ACTIVE_TEXTURE, &nn); // nn = GL_ACTIVE_TEXTURE = GL_TEXTURE0 !!!!!!

glBindTexture(GL_TEXTURE_2D, rightEyeTextureHandle);


- GL_EXTENSIONS for GL_ARB_multitexture

- tested "clean" example for multitexturing program and it work on same computer (GL_ACTIVE_TEXTURE gives GL_TEXTURE1 ...after glActiveTexture(GL_TEXTURE1));

- glActiveTextureARB

- GL_MAX_TEXTURE_IMAGE_UNITS = 20

- GL_MAX_TEXTURE_UNITS = 4

- tests on other computers (gfx ati / nvidia)

Problem is in opengl state but i can't figure where is problem.

Is there any "switch" to turn off multitexturing ?

fragment program:

#version 150

uniform sampler2D left;
uniform sampler2D right;

in vec2 UV;

out vec3 color;

void main(){
if (mod(trunc(gl_FragCoord.x), 2.0) < 0.5)
{
color = texture(left, UV);
} else {
color = texture(right, UV);
}
}

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Found solution!

Problem was in init of glActiveTexture:

PFNGLACTIVETEXTUREARBPROC pglActiveTexture = NULL;

#define glActiveTexture pglActiveTexture;



For some reason when i replace:

glActiveTexture(GL_TEXTURE1);

with

pglActiveTexture(GL_TEXTURE1);

it start working.

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Why not use glew. That way you do not have to worry about setting up all the extension.

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Why not use glew. That way you do not have to worry about setting up all the extension.

Because i'm writing mod to game, and everything i do, is in intercepted SwapBuffer.

I do not load any libs.

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You can statically link to GLEW and not need to load any libs.

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