First add two PostProcess Volumes, one will be a clean version, the other will have the full effect.
I’m going to fade in a Crosshatch and outline effect so I have my PP volumes like this:
The PostProcessVolumeCrosshatched PPvolume has 2 x PostProcess Material Instances like this:
The PostProcessVolumeUncrosshatched is like this.
The initial setting of the level shows a clean version- no effect, so the PostProcessVolumeCrosshatched has its Array Blends set to 0
Both PP volumes have Material Instances of a Post Process material.
In the Master Material I’ve got it set like this: A SceneTexture:PostProcess0 is attached to the A input of a Lerp. This is a clean with no effect.
All the PP effect stuff comes in on B. There is a parameter attached to control the Lerp Alpha
I made two Material instances for each Master Material. The ‘full-effect’ versions have the LERP alpha parameter set to 1. The ‘clean’ versions have the LERP alpha parameter set to 0 – so no effect.
I use the ‘full-effect’ versions of the material instances in the PostProcessVolumeCrosshatched and the ‘clean’ versions in the PostProcessVolumeUnCrosshatched
In my Level Blueprint I fade out the PostProcessVolumeUnCrosshatched like so. The Target is set to 0. I found I needed a clamp as the values seemed to jump to 1 without it.
I don’t know if i want to fade in other effects how this will work,