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is there an expression to change opacity of an image...

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dan jacobsen
is there an expression to change opacity of an image...
on Dec 8, 2008 at 2:12:03 pm

hi all,

if you have an image in an action, is there an expression you can add to transparency so that the image will 'turn off' when facing away from the camera?

ie: useful for 2 images forming opposite sides of a turning page.

or any other way of doing it except manually animating the transparency?

cheers



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moody glasgow
Re: is there an expression to change opacity of an image...
on Dec 8, 2008 at 6:33:51 pm

So basically you want transparency to be 100 when y rotation >90 ?
I don't use expressions alot, but I think this would work:

Click on your transparency in animation.
click on expression.
type in:
if((axis1.rotation.y)>90, 100,0)



moody glasgow
smoke/flame


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chee keong hiu
Re: is there an expression to change opacity of an image...
on Dec 9, 2008 at 11:12:48 am

turn on the Z-buff (in setup), then put your behind picture just 1 pixle (in position Z)behind the front picture, that will do.

my autodesk tips & tricks
http://mysmoke.blogspot.com

ckeong


Thanks
Ckeong


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dan jacobsen
Re: is there an expression to change opacity of an image...
on Dec 11, 2008 at 10:00:30 am

thx guys.

i was hoping there might be an expression that would work in conjunction with the camera. just using the rotation expression would only work with the camera at default rotation i guess.

perhaps there's a way of combining the camera rotation too? but that sounds like a 3D geometry nightmare.

on after effects there is an expression command called toCompVec and it basically returns a +ve or -ve value depending on the difference of the object and camera's vector. very, very handy. i was hoping smoke might have something similar as it doesn't have front and rear sides.

I will try the 1 pixel out thing. i was trying to avoid this as i used it on AE before i found out about the expression and it caused me a lot of errors with lights and shadows, but smoke may work better.

either of you guys have access to a smoke wish list? might be nice to add that expression on for the coders?

thanks for your help :)



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