A.D.A. Amiga Demoscene Archive

I recently found my old demo disk collections and I tested some disks on my A500. For example I watched Scoopex "Mental Hangover" and "Equipose" by Complex. And then I saw these stencil and pencil vectors (again :-)). While I think that stencils are not hard, I am a little bit clueless about the pencil vectors.
Can someone here please explain how those two vector effects work?

I've seen the terms mixed a bit (as with so many other effects) but given your examples:

Stencil: every vector face is simply used to "stencil out" a piece from a picture / texture. How nice this ends up looking all depends on the how many faces you've got, the texture itself and how you move the texture relative to the movement of the vector faces.
Da Jormas has imho had the coolest stencils on OCS. See Major Release and that thing from last years Assembly.

Timur Lenk and Fistpig were also based on a similar technique, although in 18bit chunky. :)

Pencil: Similar stuff but you instead do the masking and texture-selection per horizontal line of the vector face. Again, the magic is all in how you select each line and what your texture looks like.

Have to agree on that one, the stencils in "Major Release" looks absolutely marvelous.

Another demo with excellent stencil vectors is "Surfing Great Victoria" by Traktor.