Hi, everyone.
My simple question:
What's the difference between $PT and $ID?

One is point number and another is ID number.
They're useful in using particles.
I put it in this way to say, A Point has PT and ID, doesn't it? :roll:

Thanks for your reading.

in POPs, particles have both $PT and $ID. the main difference is that when particles die, the $PT of the remaining particles mostly will change ($PT always goes from “0” to “amount_of_points - 1”), whereas $ID remains constant. a good way to remember this is that $ID is a point attribute, whereas $PT is just the index of the point in the group of all points.


so if you have expressions that rely on some point numbering to achieve an effect (like say rand($PT) for a random number based on the point number), you should use the id of the particle instead, since that is guaranteed to stay the same (so you'd use rand($ID)).

sorry for the complicated way of explaining cheers

Your explanation is clear and great!!
You mention $PT is changed by the amount of points.
I think this is the key to differentiate between them.

Thank you and your reply.

Happy

Thanks for the explanation anamous!

Would you please more elaborate it in the easiest way? that's really complicated explanation

The particle $ID is unique to each particle, even if it dies. The $PT number (or @ptnum) is not. So if you need to tie an action to a specific particle or point regardless of how the points come and go, the @id or $ID is guaranteed to work.