纹理渲染和VBO的[OpenGL / SDL / C ++]

Question

So, I've been working on a little game project for a bit and I've hit a snag that's annoying me to no end. I load an obj file which then gets rendered after being put into a VBO. This part works fine, no problemo. However, I've been trying to get it to render the accompanying texture with the supplied UVs with no success. Currently, I just get a matte green colouration on my model. Upon investigating it in GDE, I've seen that texture gets loaded fine and occupies the GL_TEXTURE0 unit, so that's not the issue. I believe it may be my binding but I have no idea why this would fail...

void Model_Man::render_models()
{
    for(int x=0; x<models.size(); x++)
    {
        if(models.at(x).visible==true)
        {
            glBindBuffer(GL_ARRAY_BUFFER,models.at(x).t_buff);
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,models.at(x).i_buff);

            glEnableClientState(GL_VERTEX_ARRAY);
            glVertexPointer(3, GL_FLOAT,0,0);

            glClientActiveTexture(GL_TEXTURE0);

            glTexCoordPointer(2,GL_FLOAT,0,&models.at(x).uvs[0]);
            glEnableClientState(GL_TEXTURE_COORD_ARRAY);

            glActiveTexture(GL_TEXTURE0);
            int tex_loc = glGetUniformLocation(models.at(x).shaderid,"color_texture");
            glUniform1i(tex_loc,GL_TEXTURE0);
            glEnable(GL_TEXTURE_2D);
            glBindTexture(GL_TEXTURE_2D, models.at(x).mats.at(0).texid);

            c_render.use_program(models.at(x).shaderid);
            glDrawElements(GL_TRIANGLES,models.at(x).f_index.size()*3,GL_UNSIGNED_INT,0);
            c_render.use_program();
            glBindBuffer(GL_ARRAY_BUFFER, 0);
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

            glDisableClientState(GL_VERTEX_ARRAY);
            glDisableClientState(GL_TEXTURE_COORD_ARRAY);
            glDisable(GL_TEXTURE_2D);
        }
    }
}

And my shader files...

Shader.frag

uniform sampler2D color_texture;
void main() {
    // Set the output color of our current pixel
    gl_FragColor = texture2D(color_texture, gl_TexCoord[0].st);
}

Shader.vert

void main() {           
    gl_TexCoord[0] = gl_MultiTexCoord0;

    // Set the position of the current vertex 
    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}

And yes, I know I'm currently being horribly inefficient with my render loop :P but I'm already planning on refactoring it, I am just attempting to get this single model to draw correctly with everything I'm aiming to do. I have no clue why it wouldn't be rendering with the texture correctly applied - unless it's because I need to interleave my arrays but I'm still supplying it with uv data so I don't see why it fails.

Answer 1

The call that set the sampler uniform shall not set GL_TEXTUE0, but actually 0.

Indeed:

glUniform1i(location, 0)

---

For setting up a sampler uniform do:

glUseProgram(progId);
// ...
glActiveTexture(GL_TEXTURE0 + texUnit);
glBindTexture(texId);
glUniform1i(texUnit);

The main concept is that the uniform variable are a shader program state (it is mantained until you re-link the program or reset the uniform value). Without binding a program, glUniform1i shall fail since there's not shader program at which it can set the uniform value!

---

As a general advice, call glGetError after each OpenGL call to detect these conditions. Most of those calls can be removed by preprocessor in release version.

Answer 2

Well, found out that the big issue was that while I was binding a texture, I wasn't actually setting it in a way that it was understood as being used. Setting glClientActiveTexture(GL_TEXTURE0 + texUnit); in combination with glActiveTexture(); ended up being the final solution.