How to sample one side of the curve

[George1]

Hi, i have a curve that i project on a mesh and i want to select the mesh on one side of the curve (i want to make the side that have arrows to be white) i have tried the setup in the image but it give me that colors. and did not work.

any help appreciated

[stray]

Hello!
So, by finding that Cross Product, you now have a vector that points to one ‘side’ of the curve in Z-plane (regardless of curve Normal, which is also a vector that points to one side of the curve).

Now you need to compare this vector / direction to point position relative to curve, to figure out if it’s on this side.
In other words, sample nearest curve Position and subtract from current Position.
Dot Product of these two vectors will tell if they are pointing in generally the same direction or not.

Like this:

…if I understood your questions correctly.

[George1]

yes that’s exactly what i wanted ! thank you !!