CollisionTime issue (always -1)

#1

Hi there,

I just started to learning Maya and Dynamics one moth ago. Recently I am working on make some flying arrows collide with ground. I tried to use expression to make the arrows stay as the same direction (velocity) when they hit the ground. After trying many times and failed. I use the numeric in particle render type option to debug, then I found out the collisionTime of my particles are -1 all the time except the moment they hit the ground. (as the attached pic)

I had try to build my models several times, using goal or emitter drive the partices and still not undertand what’s wrong.

Any help would be much appreciated!

PS: I also uploaded the ma file to https://drive.google.com/file/d/0B1w0wTvIc49TVnFuT2hUaWtHQlE/edit?usp=sharing .

#2

Hey,

Just want to share how I solved this. (or avoid this)
Instead of using the “CollisionTime” attribute, You can either use:

1. mag(particleShape.velocity)

or

2. create an event in “Collision Event Editor”, then you can use the “Event” attribute in your expression.

cheers,

:slight_smile:

#3

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