Java – opengl rendering to texture coordinates

I want to be able to render to textures (for shaders, fonts), but I have a problem with correctly positioning quads (the frame buffer itself does what it should do) The resulting (copied) texture is displayed in the upper left corner in most cases, and the rest is cropped This is even worse for rectangular textures and has little effect on square textures (so I haven't realized this behavior for days)

Example code:

public Texture copy(final Texture tex) {
    final int tempTex = glGenTextures();
    Draw.bindTexture(tempTex);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_2D,GL_RGBA,tex.getImageWidth(),tex.getImageHeight(),GL_RGB,GL_UNSIGNED_BYTE,(ByteBuffer)null);

    // Adjust projection matrix
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    glViewport(0,tex.getImageHeight());

    // Change blendmode to ignore the transparent background
    Draw.blendingMode(GL_ONE,GL_ONE_MINUS_SRC_ALPHA);

    // Prepare fbo,add the texture as backend and clear it
    final int fbo = glGenFramebuffers();
    glBindFramebuffer(GL_FRAMEBUFFER,fbo);
    glFramebufferTexture2D(GL_FRAMEBUFFER,GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D,tempTex,0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // Finally draw
    Draw.bindTexture(tex.getId());
    glBegin(GL_QUADS);
    {
        glTexCoord2f(0,0);
        glVertex2f(-1,-1);
        glTexCoord2f(1,0);
        glVertex2f(1,1);
        glVertex2f(1,1);
        glTexCoord2f(0,1);
        glVertex2f(-1,1);
    }
    glEnd();

    // Unbind framebuffer
    glBindFramebuffer(GL_FRAMEBUFFER,0);

    // Reset projection matrix
    glViewport(0,1920,1080); // TODO Don't hardcode
    glPopMatrix();

    return new Texture(tempTex,tex.getImageHeight());
}

Sample image:

The upper is the original image rendered below the copied version

What on earth did I do wrong?

Update: now it looks like the texture has been downsampled

Solution

You should not pass the actual texture width and height to textcoords The texture coordinates range from 0 (bottom and left) to 1 (top and right) You do not hard code the actual texture size into texture coordinates

Try replacing getWidth / getHeight in the textcoord function with '1'