Particles stick to moving surface

[Irongraft]

hi guys,

I've emitted particles (bound to a VRayMetaball) from two spheres, which are initially overlapped since I want them to emulate a cell division. Attached three frames.

As you can see, at frame 981, that is when one of the two spheres is moving away from the mother cell, the particles surrounding it move slower than the sphere itself, then for a few frames, I see a piece of surface without particles on it. In other words, particles follow the attached surface, but move slower. Spheres are goals for the particles. I've set this script at creation:

cells_nParticleShape.goalU = cells_nParticleShape.parentU;
cells_nParticleShape.goalV = cells_nParticleShape.parentV;
cells_nParticleShape.goalPP = 1;

and set the parameter "conserve" to 1, but with now success.

I am not sure if what is missing to let it work is any setting from the VRay or Maya sides. I am batch rendering.

Thanks for any help

[tashko.zashev]

Hi,

Can you pack and send the scene to support@chaosgroup.com for investigation? Thank you.

[Svetlozar Draganov]

This doesn't look like a V-Ray issue at first glance.
The actual particles do not follow the sphere's surface and this is the reason why the generated metaballs are away from the geometry.
I am not really into Maya particles and I don't know what's the issue here, I'll try to find someone who has more knowledge on the subject and will be able to assist with this case.
It would be a good idea to post this into Autodesk's Forums, the guys there should figure it out quickly.

[Irongraft]

Hi Svetlozar,
thanks for your reply. If you could find anybody that may help, I'd be grateful.
Already posted in the Autodesk forums, but nobody replied so far.

Thanks in advance

[Svetlozar Draganov]

OK I think we figured it out, it looks like it is necessary to have particles caches to disk in order to render a sequence properly.
I just did that and I can confirm that everything works fine.
To cache the particles select them and go to FX menu, nCache>Create New Cache>Nobject

Select cache dir and cache name, hit Apply and wait for the caches to be stored to the hard drive.
Once completed you should be able to render the frames without that defect.

[Irongraft]

Ohh GREAT!!!
You are the only one managed to help me!!

Thank you so much. This evening will try your solution.

[Irongraft]

Hi Svetlozar,
I followed your suggestions and cached particles. Since I usually render on a HPC server with VRAY Standalone with this command line:

/vray -sceneFile="/mnt/scratch/movie.vrscene" -display=0 -displaySRGB=1 -imgFile="/mnt/scratch/render-bfx/bfx_..png" -frames=975-1015

after having exported the vrscene file, how to bring and include/import cache files that I've now generated in the folder: "cache\nCache\intro_two_spheres" of my local PC?

I've given a look at the vrscene file, but I couldn't find any link to these cache files. Is it only possible to render with caches on the machine where Maya is installed?

Thanks again

[Irongraft]

(sorry for flodding with messages)

caching seems to partially solve (attenuate the problem). Look at the stills. Left (old still) - right (new still after caching).



There should be still something missing...

Tom

[Irongraft]

Hi Guys,
finally it looks like I made it.
After a long trip, I've learned that when particles are attached to surfaces that move very quickly, you must increase the over samples (FX combo box. nCache > Edit Oversampling or Cache settings). It suffices for me to increase to 2.
In addition, under the "Solver attributes" of the nucleus node, I've set the Timing Output to "Subframe". (not sure if this was essential)
Under the Dynamic Propeerties of the particle node, I've lowered the "conserve" attribute to 0 (maybe boring, but it was necessary).

That's all