Metaballs - scaling with age

[crovfx]

Hi everyone,

firstly I would like to say that I've seen some truly wonderful work on this forum and as a transferring Maya -> Houdini artist many times I was left in awe; Houdini truly is a way of thinking. For now I had more luck drawing on my shake node based experience than on years of actively using Maya Now I am presented with a problem of creating a dusty trail; I went through the fx tools heavy smoke setup but I still do have a question because I am not clear on this:

How to scale the metaballs radius based on particle's age. I have some ideas, but again, my knowledge of Houdini operators is still very limited so I'll better keep quiet .

Also, what would be the recommended way of shading the metaballs once the motion is done, taking into account life opacity etc.

Thank you everyone and hopefully one day I'll be in the position to return the favour

Best regards.

- P.S. - All Maya fluids, FumeFX & Realflow questions are welcomed (willing to send you a setup if necessary).

[aracid]

hey crovfx

welcome to odforce, glad u like the tool

regarding the scaling issue, the trick here is too use the $LIFE in the pscale variable.

and u can do this with the point sop.

so basically, place a point sop after ur particle sim and before ur copy sop, and make sure u have the pscale parameter set too $LIFE.

an alternative would be using 1-$LIFE or any function that uses $LIFE as a lookup to modify the scale.

alternatively, take a look at the particle fluid surface SOP, thats great for surfacing fluids

hope this helps

brian

[crovfx]

Hi Illusionist,

thank you for your very fast reply; it worked like a charm and I am in debt. Really I mean it, anytime you have any questions in connection to any Maya stuff I will share my experience and do my best to try and return the favour

Kind Regards,

crovfx

[Netvudu]

Hi Illusionist,

thank you for your very fast reply; it worked like a charm and I am in debt. Really I mean it, anytime you have any questions in connection to any Maya stuff I will share my experience and do my best to try and return the favour smile.gif

As an initial favour you could start by calling him aracid instead of illusionist, hahah

Keeping on with what aracid was hinting and taking into account his Houdini knowledge swiftly kicks my a$$ anytime, you would do a great favour to yourself if you work into the concepts of variables and attributes as solely those concept will make half of the way for you in your Maya-Houdini transition. Most SideFx tutorials use them as it

Edited May 8, 2008 by Netvudu

[crovfx]

He, he...Illusionist...unbeliavable how long has it been since I've actively participated on a forum; growing old I guess - can't differentiate between ranks and usernames

Thank you for the advice Netvudu; gotta swing by your tavern for an ale

All best

[doc]

regarding the scaling issue, the trick here is too use the $LIFE in the pscale variable.

You might also consider using chf("../lookup"($AGE*$FPS) instead of life.

I often find that during the course of a shot I have to

change the life span of my particles. This will

change the value of $LIFE as it will adjust to the new

lifespan. If I use $AGE*$FPS you won't have this problem.

chf() is an expression that looks into another channel at

a specified frame to retrieve a value. It's kind of

like set driven key in maya. type:

exhelp chf()

in a texport to get the details.

usually I'll just make a spare channel called "lookup" and

refer to that. Another advantage of doing it

this way is that you can control the "falloff" of

your pscale.

hope that helps

[crovfx]

Thx a lot for Doc, as you've said it's much more convenient as I don't have to change the expression if do any changes to the lifespan.

Thx & all best