PxMaterialFlag

Defined in include/PxMaterial.h

struct PxMaterialFlag

Flags which control the behavior of a material.

See also

PxMaterial

Public Types

enum Enum

Values:

enumerator eDISABLE_FRICTION: If this flag is set, friction computations are always skipped between shapes with this material and any other shape.

enumerator eDISABLE_STRONG_FRICTION

Whether to use strong friction.

The difference between “normal” and “strong” friction is that the strong friction feature remembers the “friction error” between simulation steps. The friction is a force trying to hold objects in place (or slow them down) and this is handled in the solver. But since the solver is only an approximation, the result of the friction calculation can include a small “error” - e.g. a box resting on a slope should not move at all if the static friction is in action, but could slowly glide down the slope because of a small friction error in each simulation step. The strong friction counter-acts this by remembering the small error and taking it to account during the next simulation step.

However, in some cases the strong friction could cause problems, and this is why it is possible to disable the strong friction feature by setting this flag. One example is raycast vehicles that are sliding fast across the surface, but still need a precise steering behavior. It may be a good idea to reenable the strong friction when objects are coming to a rest, to prevent them from slowly creeping down inclines.

Note: This flag only has an effect if the PxMaterialFlag::eDISABLE_FRICTION bit is 0.

enumerator eIMPROVED_PATCH_FRICTION

Whether to correct the friction force applied by the patch friction model to better match analytical models.

This flag only has an effect if the PxFrictionType::ePATCH friction model is used.

When using the patch friction model, up to two friction anchors are generated per patch. The normal force of all contacts in the patch is accumulated and equally distributed among the anchors in order to compute friction forces. If this flag is disabled, the legacy behavior is active which produces double the expected friction force in the case of two anchors, since the full accumulated normal force is used in both anchors for the friction computation.

Note

At a future point, the PhysX SDK will always behave as if this flag was set and no longer support the legacy behavior mentioned further below. At that point this flag will be removed. Until then, it is highly recommended to always set this flag to adapt to the corresponding friction behavior (note that this flag is currently raised by default when creating a PxMaterial).

enumerator eCOMPLIANT_CONTACT

Deprecated:: This flag has no longer any effect, and will be removed in a future version. Do not use. Compliant contact behavior is now active whenever a negative restitution value is set.

enumerator eCOMPLIANT_ACCELERATION_SPRING

If this flag is raised in combination with negative restitution, the computed spring-damper output will be interpreted as acceleration instead of force targets, analog to acceleration spring constraints.

The flag has no effect for non-compliant contacts (i.e., if restitution is nonnegative). In an interaction between a compliant-force and a compliant-acceleration body the latter will dominate.