Layer order changing during render...

[2100_Productions]

During the RAM preview and on the composition, everything looks fine.

When I render my project, there are layers that suddenly change order, putting the one on bottom over others.

This isn't all layers all the time, just a few, and I can't find any pattern. There are no opacity or position changes on these layers. They're 3D, but the Z position doesn't move.

Nothing I do seems to pinpoint the problem, since the composition preview (even at full) doesn't show it. I've changed some render settings to no avail.

Anyone run into this before?

[Dave_LaRonde]

That's a weird one!  I've never head of that happening.... EVER.  Sadly, we can't help you without a little help:

FAQ: What information should I provide when asking a question on this forum?

[Roei Tzoref]

Anyone run into this before?

yes. it's and old Gotcha in After effects. you will probably see this happening in the preview if you turn the master switch for motion blur. your layers are at the same plane but sometimes, and especially as a result of the motion blur, there could be a situation where one will obscure the other back and forth (because they are in the same Z position and sometimes Ae does not know which should be first... not a detailed explanation but that's it).

the solution is set the offending 3d layer a touch closer in Z position. alternatively you could use a trick to disable 3d intersection between these two layers by adding a layer style like drop shadow, and removing the video switch from the actual layer style, leaving only one for "Layer styles".

[2100_Productions]

The Drop Shadow trick didn't work for me...the 3D manipulation did for one, but not the other. Was able to solve the problem by putting together some precomps, which I guess tricked After Effects into rendering in the correct order. Thanks!

[Mylenium · Accepted solution]

which I guess tricked After Effects into rendering in the correct order.

It doesn't "trick" anything. The render order just is this way - layer styles are always applied last, including after any motion blur and other stuff. You have to plan for this contingency.

Mylenium

[Dave_LaRonde]

Oh, you're talking about the completed animation.  I thought you were talking about the layers in the actual comp.  Never mind.