I have droned a large area and imported the Obj to Blender. It has an insane number of vertices. I want to add trees by weight painting the forest areas, but the weight painting is soooo slow. Is it possible to draw these areas in photoshop and then import the a black and white image as a “weight paint mask”? I’ve done like this with vertex paint.
You can add a low poly mesh the size of the ground and just under it. Do the weight painting on it. You can shrinkwrap it to the original ground.
You could Decimate or Remesh the original ground plane to lower the vertex count.
You can go into edit mode, select parts of the mesh and add them to the weight paint vertex group. It will be slightly less slow…
As a general working philosophy lowering the vertex count is standard for anything created with photogrammetry or scanning. Or use a low poly version as I already mentioned.
Learn Geometry Nodes. It gives you easy access to more options for scattering the trees. Including adding the weight paint using an attribute node. GeoNodes is more efficient than older methods.
Thanks Matakani. Great tips! I tried the “paint” in edit mode and it worked great 
Plan to learn Geometry Nodes, but needed a quick fix now.
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