Hi everybody, I?Lm trying to make Hair with particles and the Add op to convert the particle points to polys ( “ Skip every n points….”).All ok but when particles dies there was an artifact in the hair (the last segment of it dissapear). Someone has a trick to fix this.

If it helps, Merging the particle source with the particle points before Add fix the same problem but in the lower part of hair.

Thanks in advance.

I?Lve tried resamples and fits and don?Lt work fine.

Surely the answer is for the particles to not die? Just turn the life of the particle up and they shall always remain.

Unless I didn't understand the problem correctly.

Cheers
Marc

Imagine that the particle source is a single point, keep all default values and set initial velocity to 5, for example, and Life to 3 secs.

Go to SOP level, you have a line of moving points, the first particle (point number 0) dies at frame 75 (25 fps) so next particle (point number 1) turns into point number 0, because the first particle have died.

If you append an Add op to the particle system you can make a polygon from that particle points, so that could be one of our hairs.Look what happend when the first point of the particle system dissapears, our polygonal hair lost its last edge.

That´s the artifact I want to resolve.

I think the problem is inherent with the approach. You can't avoid that if you have particles birthing and dying. I think the solution is to only birth the points once and then keep them around forever. I don't know how you would do this for hair though as I don't know enough about POPs.

hey RED OCTOBER

in regards to the particle solution

ive recently did some work involving a solution u trying to use (with the delete sop),

however i was trying to make fibre optics grow and avoid objects and the poping is a major issue, to solve that i made one large curve connecting all the particles and then resampled the curve and then separated the separate lines with many OTL's that did the trick. then to get motion blur, i would add a trail sop.
and use the velocity (v) variable to calculate the blur.

however to have that solution for all the hairs on ur head would be crazy,

have you through about using a spring pop?

have a low detail hair system for interactive play back and then a high detail system that is swapped out via script at render time, or even bake the geometory out?
the spring is nice cause u can group the base of ur hair to any geometry.
and even run a refine on the geom after the spring pop and obcourse, the nice variety of pop,s houdini offer you, like collision and attract pop.

just off my head, thats what i would do,
then add a create attribute sop to be able to render curves in houdini

just make a “width” attr, and set the value to something desirable.

any ways

hope this helps

all the best

aracid

This recent post on the mailing list might also help is you're using springs:
http://www.sidefx.com/community/interact/mailarchive/index.php?view=WEB&msgid=40E1990B.9030605@framestore-cfc.com&perpage=20&revdate=off [sidefx.com]