View Full Version : Runtime Expressions before/after dynamics

05 May 2008, 03:51 PM

Can someone please explain to me the difference between runtime expressions BEFORE and AFTER dynimacs?

I noticed that there were no such thing in earlier versions of Maya there were only Creation and Runtime. I tried using both BEFORE and AFTER dynamics, but the effect is the same.

05 May 2008, 07:47 PM
Maya help docks:
a runtime expression. By default, a runtime expression executes each frame during playback. A runtime expression does not execute when you go to the start time (or at the time in which a particle is emitted). You’ll often create both types of expressions for a particle object—a creation expression that initializes an attribute value in the first frame, and a runtime expression that controls the attribute value in subsequent frames.

This is what the the difference is:
Run time before dynamics will not be effected by fields or collisions.

So if you were using a velocity expression and had a field effecting the paritlces, the particle velocity expression would not take the fields attributes into consideration. Same with collisions and Goals.

Run time after dynamics will be effected by fields and collisions.

Using the same velocity expression would us the fields attributes like magnitude then calculate the expression and apply the effect to the particles.

06 June 2008, 10:04 AM
Just to clarify one, two things.
Everything optimus008 said is right remember that for Runtime Before Dyn fields will be calculated afterwards. They wont be totally ignored...

And this effects velocity changing expressions only, all the other ones can be used in either one.

Maybe this was trivial, but kinda felt the urge to mention it...

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06 June 2008, 10:04 AM
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