Visual Effects Supervisor Hugo Guerra Covers How to use Nuke’s FillMat to Mask Elements With 3D Shapes
Masking when compositing is a discipline that pervasive. If you are working with a layer-based compositor like After Effects, masking elements are generally in a 2D realm. Compositors like HitFilm, Fusion and Nuke all have unified 3D spaces, so masking elements can also function in 3d space with 3d geometry.
Director and Visual Effects Supervisor Hugo Guerra covers how this all works in Nuke, showing how to mask elements with 3D geometry. Guerra explains Nuke’s FillMat material, which can be used to create 3D mattes that can occlude other things in the scene. In this case, it will be used to occlude both 3D particles and 2D elements.
Nuke’s FillMat node lets you essentially override the selected materials on a 3D model with a constant color. It’s a great way to mask elements with a holdout. FillMat can efficiently work with the alpha channel along with RGB so that you can insert it after other material nodes in the node tree.