How do I keep a billboard the same size on screen regardless of the cameras position?

[xman84]

I recently added a billboard to display a character's name into a game. It looks good except for I would like to keep the name the same size on the screen regardless of how far the camera is from other players. How can I do this?

This is a 3D game being written using OpenGL ES 2.

Any help is appreciated.

[cireneikual]

You can project the position of the players into window coordinates (using gluProject or custom matrix math) and then render name tags in an orthographic projection. I think you can also set the model-view-projection matrix's values to 1 at indices 0, 5, 10 to remove scaling. I am not sure on that one though.