Vellum Constraint Attributes, what do they all do?

[MJNorris]

Hi Everybody,

I've got a  few (hopefully) quick question about Vellum Constraint Attributes!

So I'm basically using the vellum grain solver, with a custom constraint network made in SOPs. I've been able to get what I think is correct behaviour by adding my own attributes for "type", "restlength", "stiffness", "compressstiffness" e.t.c

However I noticed that there are some attributes that the Vellum Solver seems to add, such as "pts[]", "stress", "L" & "typehash".

Not a problem so far, except when I add a SOP solver to my DOPs to dynamically add constraints these attributes are missing.

I've been able to get my constraints to work by correctly setting the "pts[]" attribute, however do I also need to be working out the "stress" and "L" values?

Are "stress" and "L" influencing the solver, or are they more like data out attributes?

Finally, do I need to worry about the "typehash" attribute?

I can't easily upload a scene while I'm at work but if you guys think it will help explain my situation better I can do it when I get home!

Thanks in advance!

 

M

[johner]

You shouldn't need to create any of the constraint primitive attributes outside of the ones created by a VellumConstraints SOP, which are all either internal to the solver, or output attributes (like stress).  The VellumSolver detects changes to the constraint geometry topology (i.e. when new constraint are added), and performs a series of operations to update the constraints, including creating those attributes.

There's an example of creating custom constraint primitives here, which shows the attributes you generally would need to create:

https://vimeo.com/340544320#t=2h8m30s

 

[MJNorris]

Thanks a lot Johner,

 

That was really helpful!