OpenGL - 2D Texture Mapping

问题

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.)

回答1:

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);

回答2:

Are all these in the same file?

static GLuint Texture;

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

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

If they aren't in the same file, well static variables will have independent copies in each compilation unit, individually initialized to zero when the program starts. Which would explain why you're binding texture #0 after the loader returned 1.

回答3:

Try using gDEBugger gDEBugger. It will let you see all the textures that have been loaded into OpenGL and provides other debugging tools as well.

回答4:

I don't see your setting a texture function. Try adding this after glBindTexture in the geometry drawing function:

glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE ); // texture function: GL_DECAL, GL_MODULATE, etc.

Try the different texture function to fit your need: GL_DECAL, GL_BLEND, GL_MODULATE, etc.

来源：https://stackoverflow.com/questions/6001951/opengl-2d-texture-mapping

标签

c++

opengl

texture-mapping