often do i have to correct distortions of image in software like photoshop before i can open them in rhino to draw off of them.
something like perspective match for 2d images would be cool.
Hello - you can of course manipulate the image via surface control points if the image is mapped to a surface as in Picture, or a material color slot - is that what you mean?
-Pascal
yes basically, but using these steps does not produce anything usable, it keeps distorting unfortunately, trimming it and trying to match the edges makes it even worse (though i thought that must have worked better at some time. not sure). pulling on one side pulls it further on the other side or it gets wonky lines suddenly, i can rebuild it but that just gets curvy in the end no straight lines.
some simple matching would be helpful, which is mostly needed to put plans which got photographed or shitty scanned etc. into perspective. here just an example with a yellow block. try pulling that into the red square…
Untitled.3dm (4.7 MB)
edit: i dont know why but trying now once more with this simple example seems to work, but it still is not reliable and i have no idea why it now works and just before not, it gave me a kinked line instead of a straight one. and keeping the edges where they belong is also very fiddly.
Subdivide your picture-surface to have more control points.
You can also subdivide “a bit” , arrange the points roughly to your wanted shape, subdivide again with more control points, arrange the points more accurately, etc etc, upon reaching whatever you need.
hi, yes i know, but for straight lines that is not going to work, i can fiddle forever to make an artistic arbitrary shape but not for plans. the lines also have to stay in proportion, rebuilding to more points does not make that easier.
Can you attach an example?
If it is a normal perspective distortion I usually just move the 4 control points and that is enough…
My example above was just… for fun…
and now again some trouble, below i almost had it,
moving the left side just a little to fill in the gap i suddenly get this,
rebuilding the render mesh hoping that will solve it results in this, so the game repeats,
after fiddling with it once more i get a round edge at the bottom…
now imagine that is a plan, i am losing my hair and in the end i am still not there. almost tossing the screen out of the window. that is not reliable. big 
if i could kind of pin 4 corners, like in photoshop where you have perspective cropping. that would be helpful.
It seems you are having low density meshes for your picture-surface object.
Which settings do you have for your rhino meshes?
that might be, trying the same thing again with a higher render mesh i end up with this funny trapezoid right away.
problem remains, i keep ping ponging the edges around i pull on one side the other moves, until i fiddle it where it kind of fits one corner gets round. right i can rebuild the surface and start fiddling each point but the relation does not work anymore.
just imagine a ground plan which has to work properly, if i start fiddling with small points the distances do not work anymore within the plan. that is an absolute no go.
