pub fn planar<S: BaseFloat, A: Into<Rad<S>>>(
    fovy: A,
    aspect: S,
    height: S,
    near: S,
    far: S,
) -> Matrix4<S> {
    PlanarFov {
        fovy: fovy.into(),
        aspect,
        height,
        near,
        far,
    }
    .into()
}
Create a planar projection matrix, which can be either perspective or orthographic.

The projection frustum is always `height` units high at the origin along the view direction,
making the focal point located at `(0.0, 0.0, cot(fovy / 2.0)) * height / 2.0`. Unlike
a standard perspective projection, this allows `fovy` to be zero or negative.
src/projection.rs