Here's basically what I'm trying to do, in psuedo-code:
. = ..()
plane = assignAnUnusedPlane()
var effectGraphic = 'some big graphic that fills the screen'
var effectMask = 'some small graphic like a circle or star'
effectGraphic.plane = plane
effectMask.plane = plane
animate(effectMask, transform = scaleX5, time = fast)
The desired effect is that the graphic would appear at the center of the screen as a small circle or star, and then quickly spread out to the full screen.
I'm currently able to achieve this, except it suffers from one of several defects: 1) I can use BLEND_ADD which looks decent, but the effect becomes translucent instead of the hard BLEND_OVERLAY that I want. 2) If the effectGraphic has no transparent pixels, I can make it work perfectly; otherwise, compositing leaves behind opaque white.