I am trying to set up perspective projection in OpenGL such that it maps exactly to the screen pixels, like we can do in orthographic projections. I can do this for specific screen sizes, for example 640x960, but cannot do it for any screen size. Below is the code I have used to set it up for 640x960 size
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
Matrix4f perspective( Matrix4f::perspective( 60.0f, ( size.width / size.height ), 0.5f, 1500.f ) );
Matrix4f lookAt( Matrix4f::lookAt( size.width / 2.0f, size.height / 2.0f, size.height / 1.1566f, size.width / 2.0f, size.height / 2.0f, 0.0f, 0.0f, 1.0f, 0.0f ) );
Matrix4f m( ( perspective * lookAt ).translate( -( size.width / 2.0f ), -( size.height / 2.0f ), -( size.height/ 1.1566f ) ) );
glLoadMatrixf( m.get() );
This works for 640x960 resolution, but does not work for any other like 1024x768. In other resolutions it does not exactly map to the screen pixels.
I want to set up perspective projection because I want to provide an ability to rotate the sprites along x and y axes too.
Seems like the problem was with the multiplication order. The above code now works fine with any resolution.