After Effects and Rendering for Flash with Alpha Channel

I was asked this question this week, and wanted to share the answer.

Question: When I render particles with an Alpha Channel and import that into Flash, there is a dark halo or weird edges around the particles, which makes compositing impossible. I am rendering out as an FLV with Alpha. What am I doing wrong?

Answer: Render with Alpha channel, but as a straight Render. This should solve your problem. This is almost always the solution to problems like this. If you don’t know about Straight Renders, I have a short tutorial called “Straight Vs. Premultiplied” That you can watch here.

There’s also a follow up tutorial called “Remove Color Matting” which may be useful to you as well, when dealing with the halo issue.

5 thoughts on “After Effects and Rendering for Flash with Alpha Channel”

  1. Yes Straight render resolves the particles issue…

    Out of the frying pan into the fire 😛

    Another Question 😛 is it possible to alot more ram to after effects and by doing that does it get rid of the “out of memory” error

    Spec of My Computer :</b core 2 duo 2.56 Ghz with 4GB RAM and a 8600 NVIDIA GeForce GT Graphics card with a video memory of 512 MB Operating System = windows XP sp2. Hewlet Packered

    Current After Effects CS3 settings : settings imply memory and cache preference settings. Maximum RAM cache size = 60% = 1.2 GB which is confusing because 60% of 4 GB = 2.4GB (is the math going wrong because i am on a 32 bit environment.. windows XP :S ) and will enabling disk cache help ?
    thanks for your help

  2. I always had a question about RAM. Disk cache is supposed to be allocated HDD space for a program or system to use when RAM is getting low. If so, why is it that programs like AE should EVER have memory problmes? Why can’t i just set 20 GB of disk cache (I have plenty of free space on my HDDs.) Even if using HDD space is slower then RAM, it’s better then a crash!

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