Cloak effects lacks visual transition

[reaperrr]

In the original games,

• not just the owner and allies, but also enemies would see the stealth effect for a little before the actor became invisible, and after it became visible.
• The distortion effect in TD would even fade in and out smoothly during the transition.
• The transparency effect in TS faded in and out smoothly during the transition, too.

[pchote]

The palette modifiers used for these effects are fundamentally incompatible with this: it's all (actors) or nothing. My compositealpha branch has some changes towards fixing this, but it is incomplete and doesn't work.

[reaperrr]

Point 1 should be relatively easy to implement, at least.

[LipkeGu]

Point 1 is that what i wrote already here: #12146 (comment)

[PunkPun]

This should be now possible with #19881

[pchote]

#18550 added the plumbing needed to implement the third point (TS smoothly fading).