error CS0234: The type or namespace name 'PostProcessing' does not exist in the namespace 'UnityEng

I’m also getting this:

Assets\AwesomeTechnologies\VegetationStudioPro\Runtime\Utility\BVHTree\BVHBBox.cs(3,13): error CS0234: The type or namespace name ‘Mathematics’ does not exist in the namespace ‘Unity’ (are you missing an assembly reference?)

This happened after importing Vegetation Studio.

My Unity version is 2019.1.14f1

It sounds like you’re missing both the PostProcessing and Mathematics packages. Vegetation Studio’s documentation likely says they are required.

You are right, thank you very much.