Cinema style dissolve

to dissolve between to images in Motion we use "Opacity"

but what if I want to dissolve "non additive" , Cinema style like so many transitions in Fcp ?

That is a tough one. I will have a play and see what i can come up with.

If you wan't that kind of transition within a Motion project it is tricky.

And you don't wan't to apply such a transition in Fcp between a Motion project and a clip in the timeline, (specially if there is an fx on it).
Or worst : apply a transition between 2 Motion projects in Fcp timeline. Because the render time in that case is a killer. You have to export first from Motion and you loose flexibility.

To achieve that kind of "dissolve" in Motion I remember applying some composite mode to a media A above media B in the same group. And, therefore, getting an image that would be "the mid term " such a dissolve. With a static effect.

Then the two media are duplicated above on an other group without any compositing.

Then ... using Opacity twice. From A media to " resulting from compositing image group ", and from " resulting from compositing image group " to media B.

Of course in the above group, (without any compositing) media A & B have to be cutted and placed head to tail.

Hope I am clear