LWJGL OpenGL 不会绘制 2D 纹理

Question

I'm trying to create some code for loading and drawing 2D textures in LWJGL. Here is my code for drawing:

glfwShowWindow(window);
GL.createCapabilities();
loadTextures();
glClearColor(1f, 1f, 1f, 1f);

while (!glfwWindowShouldClose(window))
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    //draw

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

    glPushMatrix();
    glTranslatef(100, 100, 0);
    glBindTexture(GL_TEXTURE_2D, testTexture);
    glBegin(GL_QUADS);
    {
        glTexCoord2f(0, 0);
        glVertex2f(0, 0);

        glTexCoord2f(1, 0);
        glVertex2f(TEXTURE_WIDTH, 0);

        glTexCoord2f(1, 1);
        glVertex2f(TEXTURE_WIDTH, TEXTURE_HEIGHT);

        glTexCoord2f(0, 1);
        glVertex2f(0, TEXTURE_HEIGHT);
     }

     glEnd();
     glPopMatrix();

    //end draw

    glfwSwapBuffers(window);
    glfwPollEvents();
}

glfwFreeCallbacks(window);
glfwDestroyWindow(window);
glfwTerminate();
glfwSetErrorCallback(null).free();

And this is my texture loading code:

try
{
    BufferedImage image = ImageIO.read(file);
    /*
    if (image.getType() != BufferedImage.TYPE_INT_ARGB)
    {
        throw new TextureException("Invalid image!");
    }
    */
    int[] pixels = new int[image.getWidth() * image.getHeight()];
    image.getRGB(0, 0, image.getWidth(), image.getHeight(), pixels, 0, image.getWidth());
    ByteBuffer byteBuffer = BufferUtils.createByteBuffer(image.getWidth() * image.getHeight() * 4);

    for (int x = 0; x < image.getWidth(); x++)
    {
        for (int y = 0; y < image.getHeight(); y++)
        {
            int pixel = pixels[y * image.getWidth() + x];
            byteBuffer.put((byte)((pixel >> 16) & 0xFF));
            byteBuffer.put((byte)((pixel >> 8) & 0xFF));
            byteBuffer.put((byte)(pixel & 0xFF));
            byteBuffer.put((byte)((pixel >> 24) & 0xFF));
        }
    }

    byteBuffer.flip();
    int textureID = glGenTextures();
    glBindTexture(GL_TEXTURE_2D, textureID);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, image.getWidth(), image.getHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, byteBuffer);
    return textureID;
}
catch (Exception e)
{
    e.printStackTrace();
    throw new TextureException("Failed to load image!");
}

However, when I run this code all I get is a white screen. I checked the value of testTexture and it was set to 1, so I assume that's the texture's ID which makes me believe that worked, but I think there's something going wrong when drawing.

Answer 1

Two-dimensional texturing has to be enabled by glEnable and can be disabled by glDisable :

glEnable(GL_TEXTURE_2D);

If texturing is enables then the texture wich is currently bound is applied, when the geometry is drawn by the glBegin / glEnd sequences.

---

If you want to draw the geometry in window (pixel) coordinates, then you've to set an orthographic projection with. The orthographic projection can be set by glOrtho .
If you dont set the orthographic projection, the vertex coordinates would have to be in normalized device space in range [-1.0, 1.0].

In the following windowWidth an windowHeight is assumed to be the width and height of the window:

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, windowWidth, windowHeight, 0.0, -1.0, 1.0);

glMatrixMode(GL_MODELVIEW);

while (!glfwWindowShouldClose(window))
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);


    // [...]
}