GLSL Texture Mapping Results in a Solid Color

Question

I'm trying to write some basic shaders to map a ppm file to my shapes. Unfortunately, instead of a nice multicoloured texture (I'm using a stone brick pattern), I get a solid shade of dark purple.

Here's my code:
Init:

printf("Using %d: Texture shading\n", shaderType);
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &textName);
int w, h;
texture = glmReadPPM("brick.ppm", &w, &h);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
printf("W%dH%d\n", w, h);
glTexImage2D(GL_TEXTURE_2D, 0, 3, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, texture);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textName);
programID = LoadShaders("text.vert", "text.frag");

Render:

glClearColor( 0.6f, 0.85f, 1.0f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glMatrixMode (GL_MODELVIEW);
glLoadIdentity();
/*Unrelated code here*/
glUseProgram(programID);
varloc = glGetUniformLocation(programID,"texture1");
glUniform1i(varloc, textName);
glLightfv(GL_LIGHT0, GL_SPOT_CUTOFF, &cutOff);
gluLookAt (posx, posy, zoom,
           lookx,looky,0,
           0,1,0);
glRotatef(anglex,0.0f,1.0f,0.0f);
glRotatef(angley,1.0f,0.0f,0.0f);

renderTriangles(); //Renders mountains from a list using intermediate mode
                   // Yes, I know it's deprecated
glutSwapBuffers(); 
glui->sync_live();
glUseProgram(0);

Vertex Shader:

varying vec2 uv;
void main() {
    uv = vec2(gl_MultiTexCoord0.st);
    gl_Position = ftransform();
}

Fragment Shader:

uniform sampler2D texture1;
varying vec2 uv;
void main() {
    gl_FragColor = texture2D(texture1, uv);
}

Does anyone see any problems here? I can't seem to figure it out.

I tried with a basic White and Read 2x2 float, but again, I got one colour. It was a light red.

Answer 1

If you're getting a single colour for the whole object, there might be something wrong with the texture coordinates. I would try looking at them and see if they're correct. You can do that by modifying your fragment shader like this:

gl_FragColor = vec3(uv.xy, 0);

If your whole image is still rendered using one colour, there is something wrong with the way you're sending texture coordinates across. You're using some deprecated functionality (immediate mode, gl_MultiTexCoord0), maybe it's not working together as you would expect:

"Keep in mind that for GLSL 1.30, you should define your own vertex attribute." http://www.opengl.org/wiki/GLSL_:_common_mistakes

Answer 2

It looks like you are binding the texture after you have all of the other texture functions. You should put the call to glBindTexture right after the call to glGenTextures because you have to bind a texture before you can upload the image into it. The other problem is that instead of setting the uniform variable for your sampler to textName in the call to glUniform1i(varloc, textName) you should set it to 0 because that variable represents the active texture unit and you used glActiveTexture(GL_TEXTURE0);