parry3d::query::sat

Function cuboid_support_map_find_local_separating_edge_twoway

pub fn cuboid_support_map_find_local_separating_edge_twoway(
    cube1: &Cuboid,
    shape2: &impl SupportMap,
    axes: &[Vector],
    pos12: &Pose,
) -> (f32, Vector)

Expand description

Finds the best separating axis by testing edge-edge combinations between a cuboid and a support map shape.

This function is used in 3D SAT implementations where edge-edge contact is possible. It tests a precomputed set of axes (typically cross products of edges from both shapes) to find the axis with maximum separation.

§Parameters

cube1: The cuboid
shape2: Any convex shape implementing SupportMap
axes: A slice of axis directions to test (not necessarily unit length)
pos12: The position of shape2 relative to cube1

§Returns

A tuple containing:

Real: The maximum separation found across all tested axes
- Positive: Shapes are separated
- Negative: Shapes are overlapping (minimum penetration)
Vector: The axis direction that gives this separation (normalized)

§Why Precomputed Axes?

The caller typically computes the candidate axes as cross products of edges:

Cuboid has 3 edge directions (X, Y, Z)
The other shape’s edges depend on its geometry
Cross products of these edges give potential separating axes

This function handles the actual separation testing for those precomputed axes.

§Example

use parry3d::shape::{Cuboid, Capsule};
use parry3d::query::sat::cuboid_support_map_find_local_separating_edge_twoway;
use parry3d::math::{Pose, Vector};

let cube = Cuboid::new(Vector::splat(1.0));
let capsule = Capsule::new(Vector::new(0.0, -1.0, 0.0), Vector::new(0.0, 1.0, 0.0), 0.5);

// Position capsule near the cube
let pos12 = Pose::translation(2.0, 0.0, 0.0);

// Compute edge cross products
let capsule_dir = Vector::Y; // capsule's axis direction
let axes = [
    Vector::X.cross(capsule_dir), // cube X × capsule axis
    Vector::Y.cross(capsule_dir), // cube Y × capsule axis
    Vector::Z.cross(capsule_dir), // cube Z × capsule axis
];

let (separation, axis) = cuboid_support_map_find_local_separating_edge_twoway(
    &cube,
    &capsule,
    &axes,
    &pos12
);

println!("Best edge-edge separation: {} along {:?}", separation, axis);

§Implementation Details

Axes with near-zero length are skipped (they represent parallel or degenerate edges)
Each axis is normalized before computing separation
The function tests both positive and negative directions of each axis using cuboid_support_map_compute_separation_wrt_local_line

cuboid_support_map_find_local_separating_edge_twoway