Collision response between two objects

Hi @xiaojuan,

In SOFA, the component/class which describes the collision pipeline and how the contacts are handled is DefaultPipeline (alias CollisionPipeline). As it is visible in its init() method, the pipeline is very modular and needs additionnal components to be configured:

1 – A component like LocalMinDistance which describes the intersection method

2 – A component like BruteForceDetection which describes the broad phase collision detection

3 – A component which describe the narrow phase collision detection (it could be BruteForceDetection again because this one inherits from both classes BroadPhaseDetection and NarrowPhaseDetection)

4 – A contact manager component like DefaultContactManager (alias CollisionResponse). If you use FreeMotionAnimationLoop instead of DefaultAnimationLoop, the contact manager will construct a set of constraints which constitute the collision response. These constraints are solved thanks to a solver like GenericConstraintSolver then correction forces are applied (through a component like UncoupledConstraintCorrection) to avoid interpenetration between the 2 physical objects ( More information in the documentation: https://www.sofa-framework.org/community/doc/main-principles/constraints/lagrange-constraint/ ).
One important configuration parameter of the contact manager is its attribute ‘response’. The latter describe the constraint system (or complementarity problem) you want to construct when a collision is detected between 2 objects. In the case you want to handle friction, you’ll have to specify a ‘response’ like ‘FrictionContact’. It is also possible to add response-specific parameters like the friction coefficient ‘mu’ using the attribute ‘responseParams’. In case of deformable objects, the bounce force is not explicitly configurable because actually it depends of the elastic properties (Young modulus and Poisson ratio) of the 2 objects.

5 – Eventually a collision group manager. When several objects are within the same group, they cannot collide each other.

Hope it helps.

Dear @xiaojuan

I think Antonin’s advice should have helped you.
If this is fine for you we can close the topic.

Cheers,

Hugo