ICE: Emit from fast moving points

[Byron Nash]

I have an object that has an animated mesh derived from animating the source objects of a poly merge. I'd like to then emit particles from the parts of the mesh that are moving quickly. I've read that you can't get the velocity on meshes like this because they are being set every frame. I'm hoping to use the Get Data at Previous frame in a simulated ICE tree to calculate speed. Although, when I apply a simulated tree the mesh freezes and ignores the source inputs. What would be a good way to approach this? Caching or some other method to store the motion?

Thanks

Byron

[Grahame Fuller]

Is there deformation involved? Do you need to keep track of point motion or just object motion?

gray

[Byron Nash]

Mostly just point motion. I'm animating curves, extruding them, then merging them into one mesh. So, the actual animation ends up just being point animation in the modeling region.

[Grahame Fuller]

Are the extrusions animated, or do you have the same number of vertices throughout?

gray

From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Byron Nash
Sent: Thursday, August 23, 2012 01:55 PM
To: soft...@listproc.autodesk.com
Subject: Re: Emit from fast moving points

Mostly just point motion. I'm animating curves, extruding them, then merging them into one mesh. So, the actual animation ends up just being point animation in the modeling region.

On Thu, Aug 23, 2012 at 1:34 PM, Grahame Fuller <Grahame...@autodesk.com<mailto:Grahame...@autodesk.com>> wrote:
Is there deformation involved? Do you need to keep track of point motion or just object motion?

gray

[Byron Nash]

Vertex count is consistent, yes.

[Grahame Fuller]

That's good then, maybe you can use a separate point cloud to keep track of the point velocities. In its modelling region, add a particle at each of the mesh's vertex positions. In its simulation region, get the mesh's current point positions, subtract the cloud's point positions (you'll need to use Switch Context for this), use the length to set the attribute that you are using to filter the other cloud's emission (again, use Switch Context), and finally set the particles' point positions to the mesh's point postions to be ready for the next frame.

gray

From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Byron Nash
Sent: Thursday, August 23, 2012 02:14 PM
To: soft...@listproc.autodesk.com
Subject: Re: Emit from fast moving points

Vertex count is consistent, yes.

On Thu, Aug 23, 2012 at 2:07 PM, Grahame Fuller <Grahame...@autodesk.com<mailto:Grahame...@autodesk.com>> wrote:
Are the extrusions animated, or do you have the same number of vertices throughout?

gray

From: softimag...@listproc.autodesk.com<mailto:softimag...@listproc.autodesk.com> [mailto:softimag...@listproc.autodesk.com<mailto:softimag...@listproc.autodesk.com>] On Behalf Of Byron Nash
Sent: Thursday, August 23, 2012 01:55 PM
To: soft...@listproc.autodesk.com<mailto:soft...@listproc.autodesk.com>
Subject: Re: Emit from fast moving points

Mostly just point motion. I'm animating curves, extruding them, then merging them into one mesh. So, the actual animation ends up just being point animation in the modeling region.

On Thu, Aug 23, 2012 at 1:34 PM, Grahame Fuller <Grahame...@autodesk.com<mailto:Grahame...@autodesk.com><mailto:Grahame...@autodesk.com<mailto:Grahame...@autodesk.com>>> wrote:
Is there deformation involved? Do you need to keep track of point motion or just object motion?

gray

[Bradley Gabe]

Does this particle emission have to be single pass?

There are a number of ways you can do this. You could select the points of your moving mesh and plot curves from them, then use the curves to provides subframe interpolation to emit the particles.

You could emit particles from the moving mesh and in custom attributes store the emission frame and the ID of the vertex that emitted them. Then you can generate a bezier curve per emission vertex using the last 4 frames.

Or you could try whatever Grahame has in mind.