Calling glTexImage2D clears data buffer

Question

I'm using LWJGL for its OpenGL bindings and I'm trying to draw a quad with a texture. I have done so successfully, but there is a strange side-effect and I'm unsure why it's presenting itself.

The following code executes when first loading the texture (before the first render). I save the value of textureID for when I bind the texture/draw the quad. The following set-up code is taken from an SO answer found here.

int textureID = GL11.glGenTextures(); // Generate texture ID

GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureID); // Bind texture ID

// Setup wrap mode
GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_CLAMP);
GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_T, GL11.GL_CLAMP);

// Setup texture scaling filtering
GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_NEAREST);
GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_NEAREST);

// Send texel data to OpenGL
GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL11.GL_RGBA8, image.getWidth(), image.getHeight(), 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, buffer);

In the rendering loop, I draw the quad with the following code:

int texture = TextureLoader.loadTexture(TextureLoader.loadImage("/pc_run/run3.png"));

GL11.glBindTexture(GL11.GL_TEXTURE_2D, texture);

GL11.glBegin(GL11.GL_QUADS);
{
    GL11.glTexCoord2f(0.0f, 0.0f);
    GL11.glVertex2f(-hw, -hh);

    GL11.glTexCoord2f(1.0f, 0.0f);
    GL11.glVertex2f(+hw, -hh);

    GL11.glTexCoord2f(1.0f, 1.0f);
    GL11.glVertex2f(+hw, +hh);

    GL11.glTexCoord2f(0.0f, 1.0f);
    GL11.glVertex2f(-hw, +hh);
}
GL11.glEnd();

So far, this works (and is also wrapped between glPushMatrix()/glPopMatrix() calls). However, whatever I have drawn to the GLContext so far is not displayed. Removing the call to GL11.glTexImage2D in the initialization code, the sprite is not displayed, but everything else (non-textured) is displayed correctly.

Why are you loading the texture anew for each frame? This will eat up your memory in no time. textures are not garbage collected. Make the generated texture ID a class member variable and load the texture only once! — datenwolf, Aug 05 '12 at 09:26
I was just asking, because you have the the call of TextureLoader.loadTexture in the code you described as rendering code. — datenwolf, Aug 05 '12 at 21:32

score 2 · Accepted Answer · answered Aug 05 '12 at 04:21

2

You need to disable texturing (glDisable(GL_TEXTURE_2D)) for objects that are not supposed to be textured.

answered Aug 05 '12 at 04:21

Tim

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Thank you. If that is documented somewhere I've really missed big time. – Eitan Schwartz Nov 23 '13 at 15:30

Calling glTexImage2D clears data buffer

1 Answers1