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Sudden darkening of Shadows

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Tristan NietoSudden darkening of Shadows
by on May 24, 2011 at 10:50:48 am

Hi all,

Having a weird issue with 3D shadows in AE CS5. I've got a bunch of circles all casting shadows onto a white background, and then the circles all rotate 180 degress along the X axis (ie - flip over). The shadows that are being cast are all fine except when you turn on motion blur, on the frame just before they all spin - all the shadows suddenly get much darker. The Next frame they're back to normal.

It only happens with motion blur on and it's always the same fram: the one before the keyframe that makes them spin. I've disabled OpenGL, and done various other things like shuffling around the non-visible layers (cameras, lights, nulls etc) in the timeline, which hasn't helped.

Odd that it's always the frame before the keyframe. I've fiddled with the shutter phase, thinking that it was something to do with creating blur leading into the keyframe but even at +90 degrees (with a 45 degree shutter angle), it's still the same frame that causes the problem.

The circles are made up of 24 square solids with circular masks. Position and rotation on each is controlled by an expression linking it to various sliders on a Master Control Null. 2 lights (a spot and an ambient) and a 2-Node camera, plus a white 3D solid behind everything.

Anyone have any ideas what's going on?

PS - May be unrelated, but just upgraded to version 10.0.2 via adobe updater. Can't say if the problem was occurring prior to this update, tho.

Tristan Nieto
Visual Effects & Motion Graphics

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Tudor "Ted" JelescuRe: Sudden darkening of Shadows
by on May 24, 2011 at 10:58:23 am

Have you tried changing the motion blur settings to see if that changes anything?

Tudor "Ted" Jelescu
Senior VFX Artist

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Tristan NietoRe: Sudden darkening of Shadows
by on May 24, 2011 at 11:29:31 am

Brilliant! Didn't think to do that, it seems to have done the trick.

Changed the motion blur samples from 24 to 16. Initially that didn't do anything, but when I shifted the shutter phase to 90 deg the issue went away.

Not sure why it worked that time, or why the shutter phase or the motion blur settings should have any effect on the shadow opacity, but whatever... it worked.

Thanks for the hint.

Tristan Nieto
Visual Effects & Motion Graphics

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