[PD] GEM - cornerpin ?

[oliver]

hi, dear list !

i'm stuck on this:


i want to translate an image onto a quad-like surface with arbitrary 
points, just like MAX's [jit.gl.cornerpin] object or the "distort" 
translation in photoshop.

the only result on my research was to use the [polygon] object instead 
of [square]. while that comes pretty close to what i am looking for, i 
can't ssem to make it work without a prespective distortion.

i tried several settings, but didn't really succeed in getting an 
orthographic distortion without "folding artifacts" (please see attached 
patch that explains my problem. the simple task is here to create a 
trapezoid instead of a square - but as i said the points should be 
freely adjustable with true perspective skew)

please excuse my incredibly limited knowledge on geometrics,
my wording is probably totally wrong here

i guess what i'm looking for is something like a 2-dimensional [polygon].

thanks for any hints

best

oliver



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