Why does my OpenGL texture appear white?

Question

I'm trying to get an OpenGL texture to render onscreen in 2D. I know it seems really simple, but I'm an OpenGL newbie and this has been giving me some trouble.

No matter what I try, it is showing up white.

I've seen the other questions like OpenGL renders texture all white and checked everything on the checklist, but I can't seem to figure out the source, and I would really appreciate any help.

I'm pretty sure I've just made some stupid mistake somewhere, and have tried scrapping my code and rewriting a couple times.

Here is the code relevant to the window being run from the main method.

//Window is a custom wrapper for GLFWwindow
Window thirdwindow(window_width, window_height, "Three");
thirdwindow.show();
thirdwindow.setPosition(300, 300);

ThirdLoop(thirdwindow);

Here is ThirdLoop:

static void ThirdLoop(Window& win)
{
    GLuint tex = loadBMP("cat.bmp");
    auto size = win.getWindowSize();
    win.beginDraw();
    while (running)
    {
        if (win.isClosing())
            running = false;

        glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set background color to black and opaque
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);         // Clear the color buffer (background)

        DrawImage(size, tex);
        win.render();

        Update();
    }
}

And DrawImage (apologies for the odd indenting here, a copy-paste thing)

void DrawImage(const Size<int>& size, GLuint texture) {
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0, size.width, 0.0, size.height, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();

glLoadIdentity();
glDisable(GL_LIGHTING);

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

// Draw a textured quad
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f(0, 0, 0);
glTexCoord2f(0, 1); glVertex3f(0, 100, 0);
glTexCoord2f(1, 1); glVertex3f(100, 100, 0);
glTexCoord2f(1, 0); glVertex3f(100, 0, 0);
glEnd();

glDisable(GL_TEXTURE_2D);
glPopMatrix();

glMatrixMode(GL_PROJECTION);
glPopMatrix();

glMatrixMode(GL_MODELVIEW);
}

loadBMP was taken from http://www.opengl-tutorial.org/beginners-tutorials/tutorial-5-a-textured-cube/.

Have you tried running this through a GPU debugger? Something like GPU Perf Studio if you're using an AMD card; I think NVIDIA has something equivalent. — Jennifer Wilcox

Brandon Brandon · Accepted Answer · 2015-07-19T14:35:34

You can try this:

unsigned int CreateTexture(unsigned int Width, unsigned int Height, unsigned char* Pixels)
{
    unsigned int ID = 0;
    glGenTextures(1, &ID);
    glBindTexture(GL_TEXTURE_2D, ID);
    glPixelStorei(GL_UNPACK_ROW_LENGTH, Width);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, Width, Height, 0, GL_BGRA, GL_UNSIGNED_BYTE, Pixels);
    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    return ID;
}

void DestroyTexture(unsigned int ID)
{
    glDeleteTextures(1, &ID);
}

void DrawTexture(unsigned int ID, float X1, float Y1)
{
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, ID);
    glColor4ub(0xFF, 0xFF, 0xFF, 0xFF);
    glBegin(GL_QUADS);
    glTexCoord2f(0.0f, 1.0f);
    glVertex2f(X1, Y1);
    glTexCoord2f(0.0f, 0.0f);
    glVertex2f(X1, Y2);
    glTexCoord2f(1.0f, 0.0f);
    glVertex2f(X2, Y2);
    glTexCoord2f(1.0f, 1.0f);
    glVertex2f(X2, Y1);
    glEnd();
    glDisable(GL_TEXTURE_2D);
}

I use the following settings for the window:

static float angle = 0.0f;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

int w = 800;
int h = 600;
glOrtho(0.0f, w, h, 0.0f, 0.0f, -1.0f);

glMatrixMode(GL_MODELVIEW);
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 40.0f / 256.0f, 100.0f / 256.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearDepth(1.0f);

glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);


glPushMatrix();
glTranslatef(400, 300, 0);
glScalef(100, 100, 0);
glRotatef(angle, 0.0f, 0.0f, 1.0f);

if (TextureID == 0)
{
    TextureID = CreateTexture(Width, Height, Pixels); //I used the ImageLoader from the comments that I posted.
}
DrawTexture(TextureID, 0.0f, 0.0f);

glPopMatrix();
++angle;

SwapBuffers(DC);
Sleep(1);

enter image description here

Why does my OpenGL texture appear white?

1 Answers