PhysX Despill is a despill node that extends the edges of your subject while preserving the original edges. The way it works is that using your matte and your cleanplate, it premults your subject with an IBKGuizmo, then separately it extends the edges of the subject using an inpaint node before merging the original premulted image onto the edge extended one, while making sure not to change the luma values of the image. This way you keep the original edges of your subject but you still extend it's edges. This allows the preservation of details in the few pixels around the edges of your matte. It is very powerful as an edge despill.