12-12-2023, 08:13 AM
(This post was last modified: 12-12-2023, 08:13 AM by josemendez.)
(12-12-2023, 06:42 AM)whatever Wrote: I want to have mathematical/statistical ways to define deformation of a softbody and use that to make decisions. For example, I want to tell the difference between when it bends sideways or twists around. Like, maybe a sideways bend is a 0.5 and a twist is a 0.2, or something like that.
Examining the deformation matrix of each shape matching cluster will give you this information.
Quote:[...] I believe the calculations done behind the scene to confine the softbody to these constraints might hold the values that I am looking for. Is there a mathematical model that you are basing them on?
Yes, we use oriented shape matching constraints:
https://matthias-research.github.io/page...ticles.pdf
(12-12-2023, 06:42 AM)whatever Wrote: I know 'Position Based Dynamics' algorithm (Müller et al., 2007) is being used for simulation but does PBD also include definitions for all the constraints used in the obi solver or were other mathematical models also used? Can you please recommend the papers or keywords that can I look for understanding these constraints?
A comprehensive list of all papers used in Obi is publicly available in our webpage:
http://obi.virtualmethodstudio.com/references.html
(12-12-2023, 06:42 AM)whatever Wrote: Taking an example of bending constraints, let's take a look at the Execute(int i) function of BurstBendConstraintsBatch.cs. The variables bendVector, bend, constraint, compliance and dLambda are used. Are there any standard definition for those? Do they come from any specific model or paper?
Constraint, compliance and lambda are standard values shared by all XPBD constraints. See:
https://matthias-research.github.io/page...s/XPBD.pdf
bendVector and bend are specific to bend constraints:
https://www.researchgate.net/publication...d_Dynamics
(12-12-2023, 06:42 AM)whatever Wrote: Finally, do all of these constraints make sense for softbody. I see in documentation that density and chain are used specifically for fluid and rods. Is density properly defined for Obi Fluid asset only and I need to use it or can I play around with this constraint with softbody and see some effects?
No, not all constraints make sense for all actors. Density only makes sense in the case of fluids, shape matching only makes sense in the case of softbodies, distance only makes sense for cloth and ropes, etc. The description of a very similar, albeit simpler implementation of a unified particle system using PBD can be found here:
https://mmacklin.com/uppfrta_preprint.pdf
kind regards,