full_projection_transform is the multiplication of view_matrix and
projection_matrix. Thus, passing (view_matrix, projection_matrix) is
equivalent to (view_matrix, full_projection_transform).
Passing projection_matrix as arguments to rasterize_gaussians enables
to get intrinsics informations in the rendering code. Since we'll need
central point (cx, cy), this is the aim of this refacto commit.
Signed-off-by: Matthieu Gendrin <matthieu.gendrin@orange.com>