This is a paid asset, but now you can download Per-Vertex Ambient Occlusion And Indirect Lighting Generator Free.
Detail this asset from Unity Store: Original Link
Per-Vertex Ambient Occlusion And Indirect Lighting Generator v2019.2 (Latest version)
Tool for fast generating per-vertex
Ambient Occlusion and Indirect Lighting.
Includes two types of Ambient Occlusion solvers:
1) Raycast – calculates physically correct results with controllable ray count per vertex. Runs on any device.
2) Occlusion Render – algorithm can interact with environment objects. Requires render textures support.
Both solvers support ‘dirt texture’ with controllable shadow color and intensity.
Indirect Lighting is generated optionally from custom cubemap or from scene skybox.
Works in editor and run-time.
For Unity 4(Free and Pro) and Unity 5.
Editor tool saves generated data inside mesh vertex color and instantiates ready to use prefab inside scene. Can handle gameobjects with any complex hierarchy.
Run-time script returns generated data as per-vertex Color array.
Package includes vertex color shaders with Mobile(Unlit and One Directional Light), Legacy and Standard lighting models.
Shaders are Curved World compatible.
More info and benchmarks on forum: Forum.
Documantation and example scenes inside package.
Tool is already included in Mesh Materializer asset.
Scripts are packed in dll.