Bullet D6 Constraint or Similar?

[Alex Lombardi]

Is a way to control axis limitations in a Houdini Bullet Constraint?

 

I'm just getting familiar with Houdini implementation with the bullet solver and I am only seeing Glue and Spring types, with use of the Constraint Network. I take it the RBD Angular Constraint doesn't work with Bullet and the Constraint Network workflow in 13? 

 

Cheers

[cwhite]

You can use hard constraints with constraint networks as well - the Chains example file for the constraint network DOP (http://www.sidefx.com/docs/houdini13.0/nodes/dop/constraintnetwork) demonstrates how to use pin constraints in a constraint network. For an angular pin constraint, you just need to set the 'constraint_type' primitive attribute to 'rotation'. For more control, you can also use the 'condir' and 'condof' attributes on the anchor points to restrict the number of degrees of freedom (these attributes are documented in the constraint network's help card)

[Alex Lombardi]

Thanks Cameron,

I overlooked the Hard constraint type...though the help card got me a little confused about the condir&condof.

 

condir: Class-Point Type-Vector

If the number of constrained degrees of freedom is 1, this value defines the normal of a plane that the object can move along or rotate in. If the number of constrained degrees of freedom is 2, this value defines an axis that the object can move or rotate about.

 

 

condof:Class-Point Type-Int

 

Identifies the number of constrained degrees of freedom for an anchor (0 to 3).

 

I've taken the chain example scene and set s@constraint_type = "all" , as I want the position constraint as well, with just modifying the amount of rotation freedom.

 

I just cant seem to wrap my head around the help cards explanation though. condir looks up conof's integer value from 0-3? How does condir define the vector value with a conof's value of 0 or 3, as it only mentions 1 &2 ?

 

Lets just say I want the constraints to limit the rotations on the chain to 15 degrees in all axis, how would I go about write the condir and conof attributes, in a new wrangle node?

 

Cheers