AWS Thinkbox Discussion Forums

Geometry question

Frost
#1

Hiya,

I’ve got a question about using geometry as the particle source when the source topology changes, e.g. an object using a vol select/delete faces combo.

When I use any kind of divergence/rotation of the particles, the rotation changes - is there any way to fix this so the rotation is static as the object builds? I’ve tried fiddling with settings, but not found anything yet.

Thanks,

Steve

#2

Hmm, odd it is like Frost is not respecting its original vertices. Like it is re-evaluating up to a certain point then stabilizes.

I posted an example, when the volume select reaches the top cap of the box, everything begins shifting.
max2011_FRST_ChangingTopo_Issue.max (552 KB)

#3

The divergence is based on the particles’ ID channel. For a geometry source, we use the vertex number to create an ID channel. Unfortunately, when the mesh changes topology between frames, the vertex number and ID can change too.

I would handle this using Krakatoa (download). We can save the vertices of a mesh with consistent topology as a PRT file. Then we can load the particles using a PRT loader, and delete particles instead of changing the mesh topology.

  1. Create the geometry you want to use as a particle source. This geometry must have consistent topology.
    brickWall_saveParticles.png
    brickWall_saveParticles.png492×783 50.5 KB
  2. Save the geometry to a PRT file using Krakatoa. Be sure to save the Position and ID channels.
  3. Create a PRT Loader, and load the PRT file you just saved. Click “Load Single Frame Only” if you saved a single frame.
  4. In the “Culling and Deformations” rollout of the PRT Loader, click “Make Culling Named Sel. Set…” and pick the box you want to remove particles from.
  5. Click “Invert-Cull Inside”.
  6. Create a Frost object, and pick the PRT loader as the particle source.
    brickWall_result.png
    brickWall_result.png633×813 33.2 KB

This seems to work for JohnnyRandom’s scene. Please let us know if this works for you too, Steve.

#4

Hi Paul,

Yeah, I suspected that might be the case -
is that something I can do with the demo version of Krakatoa, or will it work only with the full version?

I’ll probably not be able to try it tonight, as I’ve got a paying job to finish off (curses), but I’ll have a play when I get a sec.

Cheers

Steve

#5

Yes, you can do that using the free evaluation version of Krakatoa.

#6

Cool, thanks Paul

Regards,

Steve

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