Enum GroundSupport 

pub enum GroundSupport {
    Material,
    WorldOffset(Vec3),
    CylinderRim {
        axis: Vec3,
        radius: f64,
        quarter_turns: u8,
        offset: Vec3,
    },
}

How a ground support point is attached to the body that owns it.

Detection reports this per contact because the gradient of a contact depends on it: a support point that rides the body rigidly moves with Rᵀ(q), one that hangs below a curved surface does not, and one on a cylinder’s rim does neither — it moves with the axis. The convex adjoint (phyz_diff::contact_adjoint) reconstructs the support point from this, and getting it wrong is a silently wrong gradient rather than a failure.

Variants

Material

The support point is a material point of the body: a box corner, a mesh vertex, or a cylinder rim point in the degenerate upright case.

WorldOffset(Vec3)

The support hangs a constant world vector below a material point: (0, 0, −r) for a sphere or capsule dropping onto a z-plane. Spinning the body does not move it.

CylinderRim

A point on a cylinder’s cap rim: cap centre + radius · dir, where dir is the barrel’s steepest-downhill direction û turned quarter_turns × 90° about the axis (see cylinder_rim_dir).

axis is the cylinder’s axis in world coordinates at detection time. It is a body-fixed direction, so an adjoint that wants to stay exact under a perturbation freezes it in the body frame and recomputes dir from the perturbed axis — û is a function of the configuration, and holding it fixed drops the whole “the wheel banked, so its contact moved around the rim” channel.

Fields

axis: Vec3

The cylinder’s axis in world coordinates at detection time.

radius: f64

The cylinder’s radius.

quarter_turns: u8

Which rim direction this contact sits on, in 90° steps from û.

offset: Vec3

radius · dir as detection resolved it — the world offset, kept so that callers who only want that do not have to recompute it, and so that an adjoint has something total to fall back on if a perturbed axis lands inside the degeneracy.

Implementations

impl GroundSupport

pub fn world_offset(&self) -> Vec3

The vector from the material point that generated the contact to the support point, in world coordinates, at the configuration it was detected in.

Trait Implementations

impl Clone for GroundSupport

fn clone(&self) -> GroundSupport

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for GroundSupport

impl Debug for GroundSupport

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for GroundSupport

fn eq(&self, other: &GroundSupport) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for GroundSupport