Change Particle Streak Tail Size Per-particle?

[emtx]

Ok i figured out how to use ramps on per-particle opacity - Does anyone know if you can do this with the tail size on streaks?

This is kind of following on from my last particle-newbie question...

How do you change particles (in my case on a curve flow) so that the older or further along the curve they get they change size or opacity etc??

also - is there a way to hide the very start of a curve flow so you don't see the messy looking bit before they start flowing along their way?

[joojaa]

Tail size is based on velocity, you could do this:

in expression after dynamics store the velocity to extra custom array, then assign your own scalings on the vectors (or directions)

in the expression before dynamics copy the velocities back so rest of dynamics work ok.

If its a curve flow you can omit step 2.

[emtx]

Thanks for the reply Joojaa.
It seems after adjusting a few other things i don't need to do that anymore - which is fortunate for me because i was somewhat stumped on how to go about writing an expression like what you suggested!

Anyway - i was wondering if you could give me some tips on render settings for multi-streaks. In a test render of my simple animation i found that increasing the samples destroyed all my streak detail and left me with a blurry thing - and samples set to 1 looks more how i want but as it moves it looks all grainy...?