offset animation based on groups

[rohandalvi]

hi,

Is it possible to offset an animation of a copied object based on when a point comes into a GROUP.

For example,

I want to show rain falling on a ground and when ever it collides with the ground , the particle comes into a new group called COLLIDE.

Now I copy a grass strand onto the COLLIDE GROUP. but lets say that I have animated the scale of the GRASS STRAND over 30 frames from 0-100% , Is it possible to offset this animation for every point so that the animation only activates when the particle becomes a part of the group.

or objects copied to a grid and when a group bounding box moves along this grid selecting the points, it triggers an animation.

I can do this in PFLOW in 3dsmax, by offsetting the animation to activate on EVENT DURATION or PARTICLE AGE.

How do I do this in HOUDINI.

I tried a few things that do work, but they are based on transferring COLOR VALUES and then multiplying $CR with the animation stored in a custom parameter, but this wont work for the above mentioned example. I could also offset based on $PT or $CY but this only works for simple stuff. I also tried multiplying with PARTICLE AGE but the strand keeps on growing, I couldnt figure out how to stop it from growing after a certain point.

with regards

ROHAN DALVI

Also, one small thing, what would be the formula to select points via a percentage value or randomly, I am not very good at math, so I dont know all the formulas.

thanks once again

[GallenWolf]

Also, one small thing, what would be the formula to select points via a percentage value or randomly, I am not very good at math, so I dont know all the formulas. sad.gif

Group SOP, under expressions you can try

rand($PT) < 0.5

rand($PT) > 0.97

rand($PT) <= 0.23

etcetc.

if you are dealing with particles, use $ID to avoid popping.

[rohandalvi]

thanks for the math,

Any Ideas as yet as to how to do the above mentioned thing. Offsetting animations based on grouping.

Or i should maybe stick to PFLOW or maybe mograph in CINEMA 4D

[GallenWolf]

It's a tad more involved in Houdini, but do-able Check the hip file. You will need to do some expressions and time shifting of the copied geo.

GW

itsRainingTubes.hip

[GallenWolf]

btw, as an ex-max user, I'd say stick with H for particles. Haven't tried the BOX tools, but I think you need to pay extra on top of 3dsmax in order to add functionality to your program (?!) I do miss Afterburn and FumeFX on max those - IMO, max has the most awesome plugins hands down.

[rohandalvi]

thanks a lot GallenWolf

This is exactly what I wanted.

I never even knew there was a TIMESHIFT SOP.

But I still cant leave MAX. As hardly anyone in India uses HOUDINI. actually I should say hardly anyone has heard of HOUDINI.

And since I mainly do Lighting and rendering, I am sort of addicted to VRAY. that not to say that MANTRA isnt powerful, but it's just that vray gives the results a lot faster And I am hardly a programmer , I am just starting to get into some amount of shader programming, but that will take while. Till then MAX is my livelihood.

I would be so cool if someone made VRAY for HOUDINI. :

VFX is something that i am only recently starting to get into, but I would agree, HOUDINI is god when it comes to VFX, thats why I am learning it. But plugins for max are pretty awesome.

Once again, thanks a lot for the file.

Also could you explain the expression you put in the TIMESHIFT SOP, why did you multiply if with $FPS and why did you use object merge.

Also usually if the CHF function to call in the animated data , how are you calling the animation into the copys op, or does the TIMESHIFT take care of that.

with regards

ROHAN DALVI

By the way, where are you located and how long have you been working in HOUDINI ?

I have been thinking of maybe developing a demo reel using HOUDINI, so what exactly would be expected, Just VFX stuff or lighitng and rendering stuff will also do.

Edited May 28, 2008 by rohandalvi

[GallenWolf]

Also could you explain the expression you put in the TIMESHIFT SOP, why did you multiply if with $FPS and why did you use object merge.

I assume you've figured out that GWHIT contains the local variable for the time that the particles hit the mesh. Basically, if you take time * frames per second, you will get the frame number.

The timeshift sop needs frames, hence this conversion.

With regards to the object merge, it's basically that - to merge in the animated tube. Why I don't animate the tube in the geo1 object is because I like to keep things compartmentalized. That's about it; you can definitely have all your networks in one object, but it could get messy.

Also usually if the CHF function to call in the animated data , how are you calling the animation into the copys op, or does the TIMESHIFT take care of that.

The copy sop copies the tubes onto the points of the particles. I've set the template group so that only the group that hits will be the copy sop's template. I then send up the hit time upstream to the timeshift in order for it to bring in the correct animation timing.

By the way, where are you located and how long have you been working in HOUDINI ?

It depends on the time of the year really. Close to 2 years now.

I have been thinking of maybe developing a demo reel using HOUDINI, so what exactly would be expected, Just VFX stuff or lighitng and rendering stuff will also do.

There are very cool reels in the demo reel section of the forum, do check them out to see what's required.

Cheers!

GW