Calculating Correct U / V For surface - Image sampler

Hi all,

Its been a little while since I’ve been GH’ing - in the depths of some hardcore delivery project in the dreaded RVT.

I was asked by a colleague who is planning a cycle if i could produce a surface based on a mapping image he has found.

I have got this working, however, this only seems to work with a specific UV setting. I’ve always found getting the correct “u” when using surface from points a bit of a dark art (/fumble)

I would have expected changing the extents x and y in this case to simply increase and decrease resolution.

Could someone please expand on why this changes the calculations so much?

Many thanks


(also 23 seems to give a believable result which matches what i had expected from the image - how could I have correctly ascertained this “theoretically”) (543.5 KB)