Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Custom Tree Importer Free.
Custom Tree Importer v3.3 (Latest version)
Custom Tree Importer v3.0
Benefits
Import manually modeled trees from Maya, 3ds Max, Modo or Blender and let them get adjusted to be compatible with unity’s tree creator shaders and directional and radial wind zones or create smoothly fading LOD groups using custom shaders which also support physically based lighting.
Add your trees using the terrain engine or place them as independent game objects.
Compatibility
CTI LOD shaders support the built RP as well as LWRP. Experimental LOD shaders for HDRP 7.1.2 and Unity 2019.3.0b8 are included.
Documentation / Documentation LWRP / Official Thread
See what others have achieved using CTI
Tropical Forest Pack
Winter Forest Environment
Rocky Hills Environment
Ancient Land
Oak Trees Package
Requirements
Please do not expect the custom tree importer to simply make any tree just work: You will have to spend some time tweaking your model.
First and foremost the custom tree importer needs trees to be imported as nested, hierarchical objects.
Hierarchical setup of the tree
In order to be able to calculate the influence of wind on the trunk, the branches and leaf planes the importer script has to know about the different parts of the tree and their origins.
For this reason you will have to provide trees as nested, hierarchical objects like shown on the screen shots attached.
The custom tree importer script works as asset postprocessor. It combines all submeshes into one and bakes the needed bending information into vertex colors and uvs.
Bending
Adjust bending on each level of your tree using control tags which let you specify its reaction to main wind, main and edge turbulence to create convincing and lively bending trees.
Advanced rendering and LOD groups
Trees imported using the custom tree importer are fully compatible with the built in tree creator shaders and also any tree shader based on these.
Furthermore this package ships with a bunch of shaders which will give you physically based shading and enable you to create smooth fading LOD groups including several mesh instances as well as real time lit billboards – all physically based shaded.
Third party support
Trees created using CTI may be used with Vegetation Studio Pro and will benefit from “instanced indirect” rendering (built in RP only).