# How to discard vertices/faces according to a geometry or texture feature?

I have a square plane mesh with applied texture (satellite image of an area) and displacement (height map) that gives an overview of a land area with some features like water which I want to remove.

Water is on the Z axis value = 0, it is also of particular color (blueish). I also have a detailed shape polygon that I could cut from the plane so only area of interest is shown.

My question is how would I proceed with removing vertices from the geometry according to their feature (Z-axis value) or texture color (color blueish)?

Alternative approach, how would I cut the plane along given polygon (taken from geojson, not aligned to plane vertex positions)?

picture for reference

• you could just use boolean modifier...with a big enough box starting at z = 0 and going -z direction. Commented Aug 18, 2021 at 7:55
• @Chris thanks for the hint,, the one issue have is that this discards also valid vertices (part of faces that are in fact terrain)
– mtx
Commented Aug 18, 2021 at 8:00
• can u show us a screenshot of your scenario? Commented Aug 18, 2021 at 8:02
• You could use the water colour (selecting for blue) or the water's height and create a mask from this selection. From there your could produce an opacity map from the mask, therefore hiding the vertices in the render. This won't remove the vertices per se, but it is a non destructive approach Commented Aug 18, 2021 at 9:24
• You need faces cut, where they are part terrain, part water? Commented Aug 18, 2021 at 10:35

Select one face in Edit mode, then Go to Select -> Select Similar -> Coplanar (or Normal). Tweak settings a bit and you should get the selection you want (at least mostly).

The only other way I could think of would be to iterate through every vertices with a Python script and have it select them for you if their Z value is < 0.001

• thanks! Coplanar with less than 0.00001 worked!
– mtx
Commented Aug 19, 2021 at 10:44
• nice to hear it! Commented Aug 23, 2021 at 12:56