How to add velocity to newborn particles

[Gabriel_Wolf]

Hello,

I started to use popvop for this project. So I would like to add velocity to the newborn particles. I took the normal of the emitter then plugged into the velocity, which is good, but in this case that will be a constant velocity. So I would like to get the newborn particles and add that velocity for example 4 frames, then they lose that velocity and simply go with the gravity force. 

I was wondering what if I add a popwrangle. The make a statement if the age of the particles is less  then 1 ( i mean second) and the velocity. else if the age is greater then 1 second then just use the gravity. Will this work? How can I write this as a prompt VEX?

Can you help me?

Thank you.

Edited August 13, 2019 by Gabriel_Wolf

[wakimsan]

Hi Gabor, I imagine it's "drag" or "air resistance" you're after. I think it's the popWind node where you can add a specified amount of air resistance. If you play with that value and the inherited velocity, you might get what you're after:) Though, if you need control over the exact frame the particles slows down, it might not be the best way. Maybe animate the air resistance...?

With your edit, this solution is probably not precise enough. popWrangle...?

Edited August 13, 2019 by wakimsan
question changed

[Gabriel_Wolf]

Hello Joachim, 

Thank you for your help. No not exactly. it is very easy so I can explain with adding any picture. So I made a sphere, I add an animated mountain, and add a normal. Then I emit fluid from that object. In the dop I added pop vop and just set the normal to V. So I like the was how the fluid shooting out from the emitter. If i add the drag and air resistance the v still remain on every particles during the whole simulation. So that's why I want to give that velocity only particles are aged under 1 second.  Then they can fall down by the gravity

[wakimsan]

So the particles will change their trajectory completely from one frame to the other? Like colliding with a wall?
You could possibly ignore the inherit velocity and use your velocities through advection instead. But only affect a specific group of particles. In this case, if age is less than X. Then you could add another gravity force which affects the particles if age is greater than X. If you create your groups before the forces in your popnet, you should be able to simply select those for each force.

[Gabriel_Wolf]

You meant something like this?

[DonRomano]

You can use a geometry wrangle and type in 

if(f@age < ch("max_age")){
	v@v *= 2;
    }
else{
	v@v *= 1;
    }

 

[schwungsau]

or simpler. 

in source node add group name under "just born group" after you use any node (for example popvop) and use the source group name.

 

[Gabriel_Wolf]

I really thank you for your help, but there is two issues. One of them is my fault because I didn't say the proper situation. So, DonRomano, if I understand your solution well every points under some age have velocity:2, and after that age their velocity become one. Right? And schwungsau I apritiate your help too, but my english looks like not enough, because I don't understand anything of your solution. Maybe some comma in your sentence would helpful.  So I placed a sphere,then add an animated mountain node, then take it's normal and I set it to the velodity in the dopnetwork in a popvop. This time I attached pictures and the hip file too. So I would like to add that velocity  whatI get in the popvop, to the particles which's age is under 1 second ( or any value). The after the first second I want the particles to leave that velodity and just go with the default gravity force. 

waterbending.hiplc

[DonRomano]

No, its just multiplicating their velocities by 2, and otherwise by 1, so its unchanged.

I've added thing to your file, you can set the velocity in the source volume.

 

Cheers,

waterbending.hiplc

[Gabriel_Wolf]

Thank you very much. I will check it tomorrow.