This is a paid asset, but now you can download Oak Trees Package Free.
Detail this asset from Unity Store: Original Link
Oak Trees Package v2.03 (Latest version)
“If possible, please buy the package to support the developer”
This package contains a set of 6 highly detailed PBS oak trees – each consisting of 2 smoothly fading mesh based LODs and a billboard.
The trees are manually modeled, carefully optimized, support instancing and only use 2 shared materials.
The oak trees were created using CTI whose tree shaders support (deferred) translucent lighting, advanced bending driven by a built in directional wind zone and smooth LOD transitions. Unity’s spherical wind zones are supported only on manually placed game objects.
The trees have been successfully tested with Unity 5.6.3., Unity 2018.2.15 and Vegetation Studio Pro using instanced indirect rendering. A modified shader adaptor is included.
Unity’s terrain engine is fully supported.
Deferred shading is compatible with Lux Plus, AFS and ATG and needs you to assign the provided or compatible deferred lighting and reflection shaders.
The package ships with HDRP 7.1.2. and URP 7.3.1. / 7.5.1 compatible shaders and prefabs.
The vertex count ranges from 6900 / 4300 (small oak) to 11700 / 7500 (big oak).
The texture resolution is 2K (leaves) and 1K by 2K (bark).
The legacy tree creator oak trees from version 1.0 are still included.