Overview
PopcornFX projects can contain several rendering interface files, each describing a set of rendering capabilities:

When creating a project, a default Editor.pkri file is created: this is the default set of rendering features available in a PopcornFX project. Most of those features are supported by our Unity/UE4/Lumberyard plugins.
A custom engine integration PopcornFX does not have to implement every feature from Editor.pkri, only what is required by the production.
IMPORTANT: Never directly modify anything located in the Library/PopcornFXCore folder. Everything contained in that folder is subject to change when updating PopcornFX to a newer version
Unsupported features
If some features from Editor.pkri are not supported by your game engine, it’s best artists don’t have those available when creating effects.
For that, you can create custom feature sets, stripping unsupported features.
Missing features
Custom game engine integrations might need additional features (exposing new properties, per particle values, ..).
It is possible to create custom rendering interface(s) (see rendering interface editor), that will extend the list of features available in the project.
In doubt, contact support@popcornfx.com