OpenGL - 2D Texture Mapping

Question

I'm trying to render a simple texture(64x64) to a 64x64 quad. The quad itself is rendering, but, not the texture. (It's rendering a blank white 64x64 quad.)

I'm using SOIL to load the image.

static GLuint LoadPNG(char* filename)
{
    GLuint texture = SOIL_load_OGL_texture
    (
        filename,
        SOIL_LOAD_AUTO,
        SOIL_CREATE_NEW_ID,
        SOIL_FLAG_INVERT_Y | SOIL_FLAG_NTSC_SAFE_RGB | SOIL_FLAG_COMPRESS_TO_DXT
    );

    if (texture == 0)
        Log("Texture Load Error: " + string(filename));

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    return texture;
}

This is my rendering code, I may not be mapping it correctly, so that could be the issue too.

// Draw Textured Quad
static void glDrawTexturedQuad(glRectF rect, GLuint tex)
{
    // Bind Texture
    glBindTexture (GL_TEXTURE_2D, tex);

    // Render Settings
    glEnable(GL_TEXTURE_2D);
    glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glColor3ub(255,255,255);

    glBegin(GL_QUADS);

    // Top Left
    glTexCoord2f(0, 1);
    glVertex2f(rect.X, rect.Y);

    // Top Right
    glTexCoord2f(1, 1);
    glVertex2f(rect.X + rect.Width, rect.Y); 

    // Bottom Right
    glTexCoord2f(1, 0);
    glVertex2f(rect.X + rect.Width, rect.Y + rect.Height); 

    // Bottom Left
    glTexCoord2f(0, 0);
    glVertex2f(rect.X, rect.Y + rect.Height);

    glEnd();
}

Here is the rest of the relevant code. (This is really just temp code, to glue it all together for testing, I'll come up with a better solution after I get it working.)

static GLuint Texture;

static void LoadTextures()
{
    Texture = LoadPNG("filename");
}

static void glRenderTest()
{   
    glRectF rect = {20, 20, 64, 64};
    glDrawTexturedQuad(rect, Texture);
}

I've also followed all the suggestions found here It's still not displaying my texture.

I swapped out LodePNG for SOIL(Simple OpenGL Image Library), it's a bit easier to use, but still isn't working.

I added glTexEnv as suggested in the answer below, but I'm still just getting a white box, I'll try some more settings, but I don't think that was it. (Edit: Tried various flags, nothing, still just a white quad.)

hm.. I have cross-checked it with the according nehe tutorial (nehe.gamedev.net/data/lessons/lesson.asp?lesson=06) but on the OpenGL calls I could not find anything awkward. Are you sure, the Image-loading function works correctly? — Constantinius
To verify for Constantinius, auto-generating a checkerboard tends to be the easiest thing. E.g. for(every x){ for(every y) { colour = ((x^y)&8) ? black : white; } } — Tommy
Well, my error handling looks correct, and it wouldn't render a checkerboard either, but, I may just have done it wrong too, I basically copy pasted it to get it done quickly. // csc.villanova.edu/~mdamian/graphics/notes/GLTextures/… — TheMonster
Could my quad be backwards, I'm hacking a game, so I don't know what kind of world system it's using, perhaps flipping the quad over? — TheMonster
If you say, that you can see your quad, but only without the texture, that would not change a thing I guess. Btw what you mean is back-face culling, which you can turn off, by typing glDisable(GL_CULL_FACE);. — Constantinius

Pete Pete · Accepted Answer · 2011-07-20T12:52:26

have you tried calling

glEnable(GL_TEXTURE_2D);
glBindTexture (GL_TEXTURE_2D, texture);

before

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

OpenGL - 2D Texture Mapping

4 Answers