- Edited
Character Generator — MakeHuman
Allows you to save the result (human figure) in different formats or export directly to Blender.
MH into Godot tutorial
Part 2
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Building Creation — Sweet Home 3D
You can export a building in .OBJ format.
Gallery
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Tree Generator — Tree It
Allows you to save the result in different formats.
Now paid, but the free old version is still available. 
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Plant Generation Software Packages
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