Alphas from meshes?

[DNorman]

The closest I have seen to that is the video linked here:

Bas-relief from 3D objects

You can either use a displacement modifier with an image as the texture or use the texture as a “brush” texture in sculpt mode. Both methods require that the base object has loads of geometry. Your video is Zbrush so it uses a texture for sculpting. Edit After watching the video it is a bit different that displacement with a texture, they are using a 3d model to make the relief. You could try this it is the most similar to the video: [Make a Sculpting Brush out of ANYTHING in Blen…

(I think it is similar to the one you linked)