group by velocity in vex H16

[craigls]

Hi, how can i group the particle with the new group expression node in H16 with vex, I tried this, but don't seem to get just the particles rising.

[sandford]

You're using the Y velocity, maybe some of those points are moving upwards as they move around?

What about using P.y instead of v? Then blast what you don't need.

I tried both v and P along with particle 'age' as another test, and my group worked fine.

[craigls]

yeah but if I use P, when the surface wave moves up and down, some points will get cut off at a certain frame, which I don't want, thats why I was thinking velocity would be the answer..

Edited May 10, 2017 by craigls

[Noobini]

might be a silly thought...but is 0.05 too big ? what about 0.001 or something an order of mag. less ?

[craigls]

tried that, but starts to cut off top of the surface of wave, tricky coz the wave is moving slowly up and down, so has some velocity, but the center moves up faster, hence my thought was to catch it with a velocity threshold, would be fantastic if i could do it with a velocity threshold within a cylindrical bounds volume.

[rich_lord]

I think you should use the magnitude of v rather than it's y component. Then it should just be a matter of tweaking the comparison number to get it right. 

I use point wrangles for most of these kinds if tasks. You would write this in one:

if(length(@v) > 0.05) {

    i@group_fastparticles = 1;

}

Edited May 10, 2017 by rich_lord

[craigls]

Thanks rich lord, that gets me close to what i need.