Particule size gradually decreases the closer it is of an objet or a dummy
Hello, I asked this question in the middle of an other thread so I thought it was more pertinent to create a new one.

I have a flow of meshed particule going down.

I want to decrease their size gradually one time they cross a spacial limit with a proximity falloff effect :

it could be either way :

- once any particule cross a surface, the particule size start to decrease lineary until zero (invisible) and we can set a time ( number of frame ) for this evolution

- the particule size gradually decreases the closer it is of an objet or a dummy , (this is the way I would prefer)

So I guess the operator to use is SCALE ?

But I tried many settings but I cannot get what I want Undecided

May be someone could put me on the track ?

- May be be I have to use a Scale operator directly in the Main Event    or   a Surface test operator in the Event 1 and use a Scale operator in an Event 2 ?

- In the Scale Operator : Timing rollout do I need to use Continuous  , or 'on event entry'

- In the Scale Operator : In the Scale Rollout, I don't know what to choose: absolute ,scale by sibling , inherit previous, relative add , relative frist , relative multiply , scale by velocity, scale by siblking distance, scale by target distance

- In the Scale Operator : In the proximity Rollout,; I don't know what to use  but this is the only place it is written  Multiply by proximity, Distance and Falloff

For convenience, Here are my files in 3dsmax 2017 -2020: the phase I'm struggling is starting frame 100 until 200
Many ways to do it, but here's a basic principle.

You use event 1 to test each particle distance, over time, and in event 2 you scale them.
Tests operator you can use:
- Object test (will test the distance of the particles, according to the pivot of the selected object)
- Surface test (will test the distance according to the mesh (each polygon) of the selected object)
- Collision (will test collision of the particles of the selected object (if you want them to just go to the next event (and not bounce) you might want to change the collision option from bounce, to continue).

In the next event, what I usually do is to animate (with autokey) scale (absolute mode) to go from 100 to zero, in let's say, from zero, to 50 frame. That way, when ty icon is selected, I can very quickly adjust the duration of the scale, by moving keyframe from 50, to any other position to make it slower or faster (you don't need to move first keyframe at zero)
Next in the scale operator i go to keyframes tab, and just change to event age, and then I check if it is set to continuous. 

So that should work.
Thank you d4rk3lf, you have been very helpfull !

I managed to get what I want, at least in a simple brand new scene from scratch.
I think I don't really understand all what is showing front of my eyes but it will get the work
In fact I struggled mostly in the proximity rollout (now I don't use it with your method)
What is rather strange are the values needed to decrease from the same size entry to the end, I'm going from 100% Scale value to 85% so the particule is almost invisible, I was expecting 0% instead of 85 % but it works so Wink

here is my file :

I figure I have to improve my understanding of the basics parameters between differents operators (like timing , on event entry , continuous , event age etc. .)

so I'm still a noob (but I started using tyflow 10 days ago :p ) but what I know is I really love this plugin, very impressive.
No problem Smile
Glad to help.

Quote:I figure I have to improve my understanding of the basics parameters between differents operators  (like timing , on event entry , continuous , event age etc. .)

This is pretty important part, and it's very cool it exist.

Best way (I can explain), is this:
Imagine, for example "speed" operator.
If you set that operator to "on entry entry" it will add speed to the particle just once, and it will stop there. So, it will execute just the first frame, and it will ignore it afterwards. The result would be, it will push particles just little.
If you set this operator to "continious" it will execute it every frame, so your particles will be constantly moving.
In 90% you will use one of the 2 above.
The rest ones (particle age, event age... etc) are there if you want to execute operator at specific ranges... so, you don't want them maybe to start right away (from frame 0), but from frame 20 to frame 40.

The cool thing about it is that it has it almost every operator.

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