box3d-rust 0.2.1

Pure Rust port of the Box3D 3D physics engine
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174

//! Shape query dispatch: projected area, ray/shape cast, overlap, and mover collide.
//! Port of the corresponding functions from box3d-cpp-reference/src/shape.c.
//!
//! SPDX-FileCopyrightText: 2025 Erin Catto
//! SPDX-License-Identifier: MIT

use super::{Shape, ShapeGeometry};
use crate::compound::{
    collide_mover_and_compound, overlap_compound, ray_cast_compound, shape_cast_compound,
};
use crate::constants::MAX_SHAPE_CAST_POINTS;
use crate::distance::{CastOutput, ShapeProxy};
use crate::geometry::{
    collide_mover_and_capsule, collide_mover_and_sphere, overlap_capsule, overlap_sphere,
    ray_cast_capsule, ray_cast_sphere, shape_cast_capsule, shape_cast_sphere, Capsule, PlaneResult,
    RayCastInput, ShapeCastInput,
};
use crate::height_field::{
    collide_mover_and_height_field, overlap_height_field, ray_cast_height_field,
    shape_cast_height_field,
};
use crate::hull::{
    collide_mover_and_hull, compute_hull_projected_area, overlap_hull, ray_cast_hull,
    shape_cast_hull,
};
use crate::math_functions::{
    cross, inv_rotate_vector, inv_transform_point, length, min_int, rotate_vector, sub,
    transform_point, Transform, Vec3, PI,
};
use crate::mesh::{collide_mover_and_mesh, overlap_mesh, ray_cast_mesh, shape_cast_mesh, Mesh};

/// Projected area of a shape onto a plane with the given normal.
/// Used by explosions. (b3GetShapeProjectedArea)
pub fn get_shape_projected_area(shape: &Shape, plane_normal: Vec3) -> f32 {
    match &shape.geometry {
        ShapeGeometry::Capsule(capsule) => {
            let radius = capsule.radius;
            let axis = sub(capsule.center2, capsule.center1);
            let projected_length = length(cross(axis, plane_normal));
            let cylinder_area = 2.0 * radius * projected_length;
            let sphere_area = PI * radius * radius;
            sphere_area + cylinder_area
        }
        ShapeGeometry::Hull(hull) => compute_hull_projected_area(hull, plane_normal),
        ShapeGeometry::Sphere(sphere) => PI * sphere.radius * sphere.radius,
        _ => 0.0,
    }
}

/// Ray cast a shape in world (or relative) space. Transforms the ray into
/// local space, dispatches, then transforms the hit back. (b3RayCastShape)
pub fn ray_cast_shape(shape: &Shape, transform: Transform, input: &RayCastInput) -> CastOutput {
    let local_input = RayCastInput {
        origin: inv_transform_point(transform, input.origin),
        translation: inv_rotate_vector(transform.q, input.translation),
        max_fraction: input.max_fraction,
    };

    let mut output = match &shape.geometry {
        ShapeGeometry::Capsule(capsule) => ray_cast_capsule(capsule, &local_input),
        ShapeGeometry::Compound(compound) => ray_cast_compound(compound, &local_input),
        ShapeGeometry::Sphere(sphere) => ray_cast_sphere(sphere, &local_input),
        ShapeGeometry::Hull(hull) => ray_cast_hull(hull, &local_input),
        ShapeGeometry::Mesh { data, scale } => {
            let mesh = Mesh::new(data, *scale);
            ray_cast_mesh(&mesh, &local_input)
        }
        ShapeGeometry::HeightField(height_field) => {
            ray_cast_height_field(height_field, &local_input)
        }
    };

    output.point = transform_point(transform, output.point);
    output.normal = rotate_vector(transform.q, output.normal);
    output
}

/// Shape cast a shape in world (or relative) space. (b3ShapeCastShape)
pub fn shape_cast_shape(shape: &Shape, transform: Transform, input: &ShapeCastInput) -> CastOutput {
    let mut local_points = [Vec3::default(); MAX_SHAPE_CAST_POINTS];
    let count = min_int(input.proxy.count, MAX_SHAPE_CAST_POINTS as i32);
    for i in 0..count {
        local_points[i as usize] = inv_transform_point(transform, input.proxy.points[i as usize]);
    }

    let mut local_input = *input;
    local_input.proxy.count = count;
    local_input.proxy.points = local_points;
    local_input.translation = inv_rotate_vector(transform.q, input.translation);

    let mut output = match &shape.geometry {
        ShapeGeometry::Capsule(capsule) => shape_cast_capsule(capsule, &local_input),
        ShapeGeometry::Compound(compound) => shape_cast_compound(compound, &local_input),
        ShapeGeometry::HeightField(height_field) => {
            shape_cast_height_field(height_field, &local_input)
        }
        ShapeGeometry::Hull(hull) => shape_cast_hull(hull, &local_input),
        ShapeGeometry::Mesh { data, scale } => {
            let mesh = Mesh::new(data, *scale);
            shape_cast_mesh(&mesh, &local_input)
        }
        ShapeGeometry::Sphere(sphere) => shape_cast_sphere(sphere, &local_input),
    };

    output.point = transform_point(transform, output.point);
    output.normal = rotate_vector(transform.q, output.normal);
    output
}

/// Test overlap between a shape and a shape proxy. (b3OverlapShape)
pub fn overlap_shape(shape: &Shape, transform: Transform, proxy: &ShapeProxy) -> bool {
    match &shape.geometry {
        ShapeGeometry::Capsule(capsule) => overlap_capsule(capsule, transform, proxy),
        ShapeGeometry::Compound(compound) => overlap_compound(compound, transform, proxy),
        ShapeGeometry::HeightField(height_field) => {
            overlap_height_field(height_field, transform, proxy)
        }
        ShapeGeometry::Hull(hull) => overlap_hull(hull, transform, proxy),
        ShapeGeometry::Mesh { data, scale } => {
            let mesh = Mesh::new(data, *scale);
            overlap_mesh(&mesh, transform, proxy)
        }
        ShapeGeometry::Sphere(sphere) => overlap_sphere(sphere, transform, proxy),
    }
}

/// Collide a capsule mover with a shape, writing contact planes into `planes`.
/// Transforms the mover into local space, dispatches, then rotates results back.
/// (b3CollideMover)
pub fn collide_mover(
    planes: &mut [PlaneResult],
    shape: &Shape,
    transform: Transform,
    mover: &Capsule,
) -> i32 {
    let plane_capacity = planes.len() as i32;
    if plane_capacity == 0 {
        return 0;
    }

    let local_mover = Capsule {
        center1: inv_transform_point(transform, mover.center1),
        center2: inv_transform_point(transform, mover.center2),
        radius: mover.radius,
    };

    let plane_count = match &shape.geometry {
        ShapeGeometry::Capsule(capsule) => {
            collide_mover_and_capsule(&mut planes[0], capsule, &local_mover)
        }
        ShapeGeometry::Compound(compound) => {
            collide_mover_and_compound(planes, compound, &local_mover)
        }
        ShapeGeometry::Sphere(sphere) => {
            collide_mover_and_sphere(&mut planes[0], sphere, &local_mover)
        }
        ShapeGeometry::Hull(hull) => collide_mover_and_hull(&mut planes[0], hull, &local_mover),
        ShapeGeometry::Mesh { data, scale } => {
            let mesh = Mesh::new(data, *scale);
            collide_mover_and_mesh(planes, &mesh, &local_mover)
        }
        ShapeGeometry::HeightField(height_field) => {
            collide_mover_and_height_field(planes, height_field, &local_mover)
        }
    };

    for i in 0..plane_count {
        planes[i as usize].plane.normal =
            rotate_vector(transform.q, planes[i as usize].plane.normal);
        planes[i as usize].point = transform_point(transform, planes[i as usize].point);
    }

    plane_count
}