How can I repeat a 3x9 texture in OpenGL's GLSL?

I have a texture with a 3x9 repeating 开发者_如何学Pythonsection. I don't want to store the tesselated 1920x1080 image that I have for the texture, I'd much rather generate it in code so that it can be applied correctly at other resolutions. Any ideas on how I can do this? The original texture is here: http://img684.imageshack.us/img684/6282/matte1.png

I know that the texture is a non-power-of-2, so I have to do the repeating within a shader, which I do:

    uniform sampler2D tex;
    varying vec2 texCoord;

    void main() {
      gl_FragColor = texture2D(tex, mod(texCoord, vec2(3.0, 9.0)) * vec2(0.75, 0.5625));
    }

This is how I'm drawing the quad:

      glBegin(GL_QUADS)

      glColor4f(1.0, 1.0, 1.0, 1.0)
      glMultiTexCoord2f(GL_TEXTURE1, self.widgetPhysicalRect.topLeft().x(), self.widgetPhysicalRect.topLeft().y())
      glVertex2f(-1.0, 1.0)
      glMultiTexCoord2f(GL_TEXTURE1, self.widgetPhysicalRect.topRight().x(), self.widgetPhysicalRect.topRight().y())
      glVertex2f(1.0, 1.0)
      glMultiTexCoord2f(GL_TEXTURE1, self.widgetPhysicalRect.bottomRight().x(), self.widgetPhysicalRect.bottomRight().y())
      glVertex2f(1.0, -1.0)
      glMultiTexCoord2f(GL_TEXTURE1, self.widgetPhysicalRect.bottomLeft().x(), self.widgetPhysicalRect.bottomLeft().y())
      glVertex2f(-1.0, -1.0)

      glEnd()

Any ideas would be greatly appreciated.

Thanks!

Almost like you'd do it with fixed pipe. Set your bound texture's wrap mode to repeat before setting sampler uniform and texture coordinates outside 0-1 range will repeat the texture.

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

In your case, texture coordinates will be s = 0-640 and t = 0-120. Fragment shader doesn't need anything special, just normal texture2D(tex, texCoord) will do.