TP question - how to emit particles between a specific range


I dont know if the title is clear enough

I am doing an animation with a milling tool that goes on a specific route (up and down ) over an over again and everytime the tool crosses the mold it emit particles - chips of metal.
Instead of doing keyframes for everytime it cross I decided to do some xpresso that tells the emitter to start emitting when Y axis of the tool is below a given number (compare node) my problem is that I need the emitter to emit between two points (higher point an lower point), this way the emmiter is emitting particles until it reach the lower point and stop until the tool go back down the next time. I tried to find an “and” node to attach to the compare node and I have found none.

I need the emitter to emit only on the way down

Please try to help
thanks in advance


Well, for starters, under the XPresso -> System Operators -> Bool section of the X-Pool you’ll find the Bool node which can be configured for the “AND” functionality you seek. Hope that helps.


You can detect the down direction by reading the emitters velocity (Object node offers this) and check for the direction of the velocity vector. Idealy the movement is along the y-axis, in this case you simply check if the velocity is negatvie to enable the emitter.



I looked all over the help file and all over the net and I could not find how to check the object velocity. I understand what you wrote but I cant figure how to put it in the xpresso.

Regarding the “and” function, I figued that out, thanks.

Thanks for your help, guys.


The Velocity is an optional output of an object node.
But there is an easier method yet. Check this example here



Here’s my take on it with both Direction and Distance catered for.

XPresso is commented and Result nodes left in to show workings.

Björn, add it to the collection if you wish. :slight_smile:

Cheers, Alan.


Thank you very much guys, it works great now

Keep up the good work

-------- hip hip hurray to Srek ,Rantin Al and chromecity

hip hip … hurray :slight_smile:

hip hip … hurray :slight_smile:

hip hip … hurray :slight_smile:


Sounds like a dodgy legal company to me. :deal:

Cheers, Alan.


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