Making lots of progress learning Motion 3 since last week, (thanks to you guys) but came across an issue when trying to work with particles, perhaps someone could suggest a fix?
I took a targa and a tif file of the same B&W clip art image to use as the source of more particles. Both images exhibit the same problem.
These were both saved out with an alpha channel, and when I just want to put them up in the comp, I select a blend mode of "multiply", their "white" backgrounds disappear and I get just the clip art keying thru, awesome. Just as expected.
Once I make that image a particle emitter though, and apply gravity to it, you can see a faint white box around each particle generate image again, looks something like a mis-set luma key that's not quite full, and the square pattern of the edges of those images act as masks, blocking views of the particles "beneath" or "behind". The effect right now is more like trying to look thru cascading playing cards that are opaque, when what I want is playing carsd that are transparent except for the suits and number on tham. That's not the actual graphic I'm using, but i think it conveys what it is looking like.
So I guess I have missed a step somewhere or did not prepare the source graphic properly to be used in this way. Maybe th wrong blend mode? Would appreciate suggestions on which particular settings to try and tweak or what elese to do in photoshop when preparing a B&W image to be used as a particle emitter with alpha.
You can fix this by changing the alpha interpretation - go to the Media tab in the project pane, select the underlying media, then go to the Media tab of the Inspector and change the Alpha interpretation.
However, the fact that you need to apply a blend mode to knock out the background of your image tells me you don't have any transparency to start with - if you knock out your background in something like Photoshop and save as a PNG with transparency, it should come into Motion with transparency and you shouldn't need to use a blend mode at all.
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Author, Motion 4 from Peachpit Press http://www.applemotion.net