Align and position particles as if they are in a hierarchy

[Robert Chapman]

Hello , o wise and knowledgable list,

Im trying to achieve something in ICE that seems relatively straight forward, just cant seem to get my head around the offset maths needed, ive tried a few options but got nowhere yet so i'm hoping someone can see this as a simple solution thats needed. Im basically trying to get rows of particles following a path to behave as if they are in a hierarchy ,see attached pic, when the instances are in rows in a hierarchy they behave correctly on the curve, unfortunately the director wants to have individual animation offsets and variations so I need seperate instances per row for the sake of randomness, but when these guys are aligned to the curve they do not turn correctly (again see pic). is there a way to get each instance row to behave as though its in a hierarchy?

thanks in advance

Rob

[Andy Nicholas]

Hi Rob,
It's hard to diagnose what the problem is without seeing your ICE tree,
but what you need to do is for every point you need to define a row and a
column number. The row number should drive a value of U on the curve. From
this U value you should be able to get a location and retrieve the
position and curve normal. You can then set each row of particles at that
position and offset them along the normal according to the column number
to get the result you want.

Cheers,
Andy

[Robert Chapman]

Hi Andy,

thanks for the pointers, my Ice tree is just emitting from points on a grid and then using flow along curve with 'align'  ticked on to move them along the curve.  the one that works is 1 instance = one row, its when its 1 instance per character that im having trouble with aligning around the curve.

 In testing this Ive already got them to follow a curve U wich is animated in time so it moves along the curve and Ive set a unique distance from curve for each particle on the first frame and can get them to remain that fixed distance but when it reaches the curve its is just the same prob as it was before, BUT I have not tried to position them away from the curve normal - honestly I didnt know a curve had one :)  will try and give this a go.

cheers

[Grahame Fuller]

You might want to think of this as a two-cloud effect. You don’t actually need two clouds, but it makes it easier conceptually.

When you emit from the point of the grid you also emit a particle in another cloud in the dead center. The particles from the grid store the ID of this other particle as well as their offsets from it.

The other particle flows along the curve, and then the particles from the grid update their point positions based on the stored offsets, taking the tangent of the curve at the other point’s location into account for alignment.

gray
“Long live Softimage!”

From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Robert Chapman
Sent: Friday, August 27, 2010 09:26 AM
To: an...@andynicholas.com; soft...@listproc.autodesk.com
Subject: Re: Align and position particles as if they are in a hierarchy

Hi Andy,

thanks for the pointers, my Ice tree is just emitting from points on a grid and then using flow along curve with 'align' ticked on to move them along the curve. the one that works is 1 instance = one row, its when its 1 instance per character that im having trouble with aligning around the curve.

In testing this Ive already got them to follow a curve U wich is animated in time so it moves along the curve and Ive set a unique distance from curve for each particle on the first frame and can get them to remain that fixed distance but when it reaches the curve its is just the same prob as it was before, BUT I have not tried to position them away from the curve normal - honestly I didnt know a curve had one :) will try and give this a go.

cheers

[Robert Chapman]

Hi Grahame,

many thanks for your advice, ive been trying so far to get this with two ICE trees , one in the modelling stack saving all the relative offset positions from the curve U = 0  and simply keyframing the curve U value to match what I had previously.  Ive got it sorta working in my head now , just getting the tangent offset right in the ICE tree and I should be good , and learning curve normal & tangent stuff along the way is a bonus

oh and yeah - Long live Softimage!!

[Grahame Fuller]

You could also use the other particle’s velocity instead of the curve’s tangent.

gray

From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Robert Chapman
Sent: Friday, August 27, 2010 12:47 PM
To: soft...@listproc.autodesk.com
Subject: Re: Align and position particles as if they are in a hierarchy

Hi Grahame,

many thanks for your advice, ive been trying so far to get this with two ICE trees , one in the modelling stack saving all the relative offset positions from the curve U = 0 and simply keyframing the curve U value to match what I had previously. Ive got it sorta working in my head now , just getting the tangent offset right in the ICE tree and I should be good , and learning curve normal & tangent stuff along the way is a bonus

oh and yeah - Long live Softimage!!

On 27 August 2010 17:21, Grahame Fuller <Grahame...@autodesk.com<mailto:Grahame...@autodesk.com>> wrote:
You might want to think of this as a two-cloud effect. You don’t actually need two clouds, but it makes it easier conceptually.

When you emit from the point of the grid you also emit a particle in another cloud in the dead center. The particles from the grid store the ID of this other particle as well as their offsets from it.

The other particle flows along the curve, and then the particles from the grid update their point positions based on the stored offsets, taking the tangent of the curve at the other point’s location into account for alignment.

gray
“Long live Softimage!”

From: softimag...@listproc.autodesk.com<mailto:softimag...@listproc.autodesk.com> [mailto:softimag...@listproc.autodesk.com<mailto:softimag...@listproc.autodesk.com>] On Behalf Of Robert Chapman
Sent: Friday, August 27, 2010 09:26 AM
To: an...@andynicholas.com<mailto:an...@andynicholas.com>; soft...@listproc.autodesk.com<mailto:soft...@listproc.autodesk.com>
Subject: Re: Align and position particles as if they are in a hierarchy

Hi Andy,

thanks for the pointers, my Ice tree is just emitting from points on a grid and then using flow along curve with 'align' ticked on to move them along the curve. the one that works is 1 instance = one row, its when its 1 instance per character that im having trouble with aligning around the curve.

In testing this Ive already got them to follow a curve U wich is animated in time so it moves along the curve and Ive set a unique distance from curve for each particle on the first frame and can get them to remain that fixed distance but when it reaches the curve its is just the same prob as it was before, BUT I have not tried to position them away from the curve normal - honestly I didnt know a curve had one :) will try and give this a go.

cheers

[Robert Chapman]

So, in the interests of folk coming across this thread in the future , I also noticed a few posts on the list asking how to do this already when trying to figure it out, thought it'd be good to include the working compounds.  Of course this can easily be achieved by 'sticking' the particle points to the emitter and then deforming by path the emmitter - but well , this way there is more control of the particles and less overhead, ive found the stick to location to be pretty cpu intensive when the point counts rise.

Currently its in two parts the 'init' stage is to be put on a Point cloud's modelling Ice tree, and is setting all the relative offset values based upon the emitter grid's initial offset position to the start of the curve path and the main compound 'Align along Curve path' is to be placed in a simulated Ice tree.

The only caveat so far is that the curve must have regularly spaced points - I havnt figured out doing this in ICE yet, but is easy to achieve by plotted a curve from a Null constrained to the path.

Cheers

Rob