Enum PolarError 

#[non_exhaustive]
pub enum PolarError {
    Inverted,
    Degenerate,
    SingularStep {
        steps: u32,
    },
    NotConverged {
        steps: u32,
    },
}

Why Mat3Fix::polar_rotation could not produce a rotation.

The three refusals and the two iteration outcomes are separate variants on purpose: the caller’s next action is different for each, and collapsing them into one None was measured to mislead. The same crate already learned this for the conjugate gradient, where pᵀKp ≤ 0 was reported uniformly as “under-constrained” until it was split into a null space (add constraints) and a rounding floor (revisit the preconditioner or the tolerance). During this type’s own development a budget that was merely too small was read as a degeneracy and cost a round of diagnosis, which is the same failure one layer up.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Inverted

det F ≤ 0: the deformation has turned the element inside out.

There is no rotation factor — the nearest orthogonal matrix is a reflection with det = −1. Fix the mesh or the deformation; a larger budget or a lower floor will not help. Returned whatever det_floor was given, so a caller passing a negative floor still cannot receive a reflection.

Degenerate

det F ≤ det_floor: too close to singular for the caller’s policy.

Revisit the floor, or the element that produced this gradient.

SingularStep

An intermediate iterate was exactly singular, so it could not be inverted.

Distinct from Self::Degenerate because the input passed the floor: what failed is the path, not the data. Lower the floor’s tolerance for ill-conditioning, or inspect the gradient.

Fields

steps: u32

Steps completed before the singular iterate.

NotConverged

max_iters was exhausted while the change was still above the settling bound.

⚠️ The input is fine — raise the budget. Measured requirements run to 21 steps for a gradient with one singular value four decades from one, so a budget of 16 is too small for the general case; see Mat3Fix::polar_rotation for the table.

Fields

steps: u32

Steps performed, equal to the max_iters that was given.

Trait Implementations

impl Clone for PolarError

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for PolarError

impl Debug for PolarError

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

Formats the value using the given formatter.

impl Eq for PolarError

impl PartialEq for PolarError

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for PolarError