Hi Tipp! Good question! This has to do with the orientation of your surface, the U and V are flipped. I believe Rodrigo references a surface from Rhino, here's how to fix it: 1) Select the surface in Rhino; 2) type in _Dir in the command prompt; 3) hit enter; 4) select "SwapUV" from the options in the command prompt; 5) hit enter. This should do the trick. Now if the surface is generated within Grasshopper. Try this def: https://mega.nz/#!FBFFFLIA!4jTp9bbFCuXIFm7Mhkdo-Wlt5tOdS4Kq4ceY3LvXxiE Good luck! Arie