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Custom Force : Field store in PTC vs Volume ?

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Hi guys,


i was wondering what are the + / - when you want to inject some velocities into a POP / PYRO / FLIP sims store in SOP PTC vs SOP Volume.

what is the most efficient way beetween the 2 ?


first is there any real difference when you read a PTC vs a Field in DOP ?

- if i have a 100*100*100 volume that store animated vel and i read them with volumesamplev

- if i have a 100*100*100 SOP point cloud containing animated vel and i read them with a pcopen

Are there any real difference ? cause at the end i just read a direction and i add it to my force or vel field ?


i find that when you have a high rez field with detailed animated vel , volume tend to be very heavy and slow down the POP or PYRO computation even when the volume is cache. I tend to use use bake PTC cause i really find pcopen blazing fast and light ? so I generally work my field with volume but then i copy the info to a high rez PTC instead of using the volume, is this a good practice ?


Do you have any case in mind where it will NOT be the same thing to use PTC instead of Field ?


Well any hint or advise on the subject would be very cool , in other word if i build a Force in SOP , what is the

- Fastest

- Lightest

- Most accurate

Way of injecting them in DOP !


at the moment i have settle with POP Wrangle / Gaz Field Wrangle with a SOP PTC pcopen. But again i would be curious to know scenario where it will be restrictive ?


Thanks for your lights !





Edited by sebkaine

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This is a discussion I was having with my friend yesterday as he was suggesting I use a volume as a vector field for my simulation. Personally, I too have found using point clouds slightly quicker in my simulations but not a significant increase. I'm also quite interested to hear other people's opinions/experience on this.

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Thanks for your feedback Jonathan ! Could you ask to your friend to motivate / argument on his choice ? :)


2 additional argument toward ptc imo are that :

- you can use the search distance of pcopen to control the influence distance,

- you can also use the pcopen point number to sample,  in order to smooth / ponderate the field.  


Those 2 give you an extra control over what you do compare to volumesamplev where you only ask for a value at the closest voxel.


I would definitly like to discover a scenario where using volume is superior / give extra advantage over ptc ?

Edited by sebkaine

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He motivates his argument by saying that you are able to use volume modelling techniques to manipulate the vector fields in interesting ways. At the end of the day it seems to come down to personal preference, but I'm most interested in finding the most efficient way. I guess we might have to do some testing :)

I think the reason why people use volumes/vdbs is because it is compact, light and efficient, so if there doesn't need to be a high level of directability to your forces, this may be generally a better approach?

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well i don't agree with him when he say you are able to use volume technic.

in fact i work my field in volume / vdb but i don't cache them as a volume field, i transfer the voxel info into a ptc with the approximate same rez and cache this on disk.

this way i get the benefit of the volume world but :

- i am able to do play in the timeline in realtime with a highrez vector field

- display the velocities as N vector very quickly


i find that it is far lighter / faster this way , than by going with field + volume trail which i can't play in Real time.


From my test if you really want detail in your field you have to go quite high in rez with volume , and there are far heavier than PTC from my test, but i might be doing this the wrong way ?

Edited by sebkaine

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