1

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 enter image description here

mtx
  • 123
  • 5
  • 2
    you could just use boolean modifier...with a big enough box starting at z = 0 and going -z direction. – Chris Aug 18 '21 at 07:55
  • @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 Aug 18 '21 at 08:00
  • can u show us a screenshot of your scenario? – Chris Aug 18 '21 at 08:02
  • 1
    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 – James Aug 18 '21 at 09:24
  • 1
    You need faces cut, where they are part terrain, part water? – Robin Betts Aug 18 '21 at 10:35
  • @RobinBetts exactly, i tried to cut it with knife tool but this will take me ages – mtx Aug 18 '21 at 13:46
  • @Chris added the screenshot, as you can see some of vertices are z =0 but i want to keep all faces that have at least one vertex with non-zero Z axis value. – mtx Aug 18 '21 at 14:08
  • If the displacement is applied consider bisect with plane normal in z at z = waterlevel – batFINGER Aug 18 '21 at 14:13
  • .. not dissimilar to first approach here https://blender.stackexchange.com/a/121732/15543 , except use vert z . Can either make outlines for knife project, or chop the original. Please clarify, one comment above suggest keeping faces if any vert.z > 0, (easy via script) yet another suggests cutting faces (which bisect will do) – batFINGER Aug 18 '21 at 15:32

1 Answers1

2

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

globglob
  • 1,588
  • 7
  • 23