[HOpenGL] get Scale of the window in HOpenGL?
matthijs at stdin.nl
Tue Jun 2 04:13:20 EDT 2009
> Depending on what you exactly want to achieve, it might be possible to setup
> your modelview matrix and your projection matrix in such a way that you get a
> 1:1 mapping between object coordinates and window coordinates, so you don't
> have to apply the inverses.
I recently struggeled with this issue, the following reshape callback does
-- | This function is called when the window is resized
reshape s@(OpenGL.Size w h) = do
-- Make sure that our model coordinates correspond to pixels
OpenGL.matrixMode $= OpenGL.Projection
OpenGL.ortho 0 (fromIntegral w) 0 (fromIntegral h) 0 1
-- Do something funky with the viewport
OpenGL.viewport $= (OpenGL.Position 0 0, s)
I'm not 100% confident about the final 0 and 1 arguments (which specify the
bounds on the depth axis, but it works like this (specifying 0 0 didn't work
and made the last line be silently ignored!).
Alternatively, you could probably set up the projection matrix such that the
model coordinates always range from -1 to 1 in both directions. IIRC that is
what happens when uinsg only identity matrices and is the default, but I'm not
100% sure. In any case, you always need to set the viewport, AFAIU.
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