Another very small but potentially useful tool for Fusion. Using a Screen-space normals pass and a rendered or painted shader image you can generate an instant “fake” render of the object with different shaders applied.
The “Radius Scale” parameter in the MatCap node can be used to decrease the search radius for the Shader mapping in case your image doesn’t fill out the frame completely.
In the Zip file you will find a Demo Comp including the tool.
Use a higher resolution normal pass (or scale it up) and scale it down to get a better result.
(rightclick, save as..)