README
¶
coll - 2d collision library for Go
Features
- Collisions only - no gravity, rigid body handling, or complex solvers
- Is data-oriented and functional
Conventions
"Sweep" tests indicate at least 1 of the objects is moving.
The number indicates how many objects are moving. e.g., box-box-sweep2 means we are comparing 2 aabbs, both of which are moving.
"Overlap" tests don't take movement into account, and this is a static check to see if the 2 entities overlap.
plural forms imply a collection. e.g., BoxSegmentsSweep1Indexed() checks one box segment against a set of line segments.
If there is more than one collision, the closest collision is set in the h *Hit argument.
Visualization of some (but not all) functions
Box-Box overlap
Box-Box sweep 1
Box-Box sweep 2
Box-OrientedBox overlap
Box-Segment sweep 1
Box-Segments sweep 1 indexed
Box-Segment overlap
Line-Circle overlap
Segment-Circle overlap
Examples (Ebitengine)
- Clone this repository
- In the terminal, change to the examples directory
cd examples - Run a folder with
go run ./foldername. Example:go run ./box_box_sweep1
Credits
Most of these collision checks were adapted from existing open source repos:
- github.com/mreinstein/collision-2d
- youtube.com/watch?v=NbSee-XM7WA - ray-tilemap (RayTilemapDDA)
- jonathanwhiting.com/tutorial/collision - box-tilemap (TileCollider)
Documentation
¶
Overview ¶
2D Collision functions
Index ¶
- Constants
- func BoxBoxContain(a, b *AABB) bool
- func BoxBoxOverlap(a, b *AABB, h *Hit) bool
- func BoxBoxSweep1(staticA, dynamicB *AABB, deltaB v.Vec, h *Hit) bool
- func BoxBoxSweep2(a, b *AABB, deltaA, deltaB v.Vec, h *Hit) bool
- func BoxCircleOverlap(a *AABB, c *Circle, h *Hit) bool
- func BoxCircleSweep2(a *AABB, b *Circle, deltaA, deltaB v.Vec, h *Hit) bool
- func BoxOrientedBoxOverlap(a *AABB, o *OBB) bool
- func BoxOrientedBoxSweep2(a *AABB, o *OBB, deltaA v.Vec, deltaO v.Vec) bool
- func BoxPointOverlap(box *AABB, point v.Vec, h *Hit) bool
- func BoxSegmentOverlap(box *AABB, start, delta, padding v.Vec, h *Hit) bool
- func BoxSegmentSweep1(s *Segment, a *AABB, deltaA v.Vec, h *Hit) bool
- func BoxSegmentsSweep1Indexed(s []*Segment, a *AABB, deltaA v.Vec, h *Hit) (index int)
- func CircleCircleSweep2(c1, c2 *Circle, deltaC1, deltaC2 v.Vec, h *Hit) bool
- func LineCircleOverlap(raySeg *Segment, c *Circle, result *Segment) bool
- func RayTilemapDDA(pos, dir v.Vec, mag float64, tileMap [][]uint8, cellSize float64, hit *Hit) (bool, image.Point)
- func SegmentCircleOverlap(s *Segment, c *Circle) []v.Vec
- func SegmentNormal(pointA, pointB v.Vec) (normal v.Vec)
- type AABB
- func (a *AABB) Bottom() float64
- func (a *AABB) Height() float64
- func (a *AABB) Left() float64
- func (a *AABB) Max() v.Vec
- func (a *AABB) Min() v.Vec
- func (a *AABB) Right() float64
- func (a *AABB) SetBottom(b float64)
- func (a *AABB) SetLeft(l float64)
- func (a *AABB) SetRight(r float64)
- func (a *AABB) SetTop(t float64)
- func (a *AABB) Top() float64
- func (a *AABB) Width() float64
- type Circle
- type Hit
- type OBB
- type Segment
- type TileCollider
- type TileCollisionCallback
- type TileHitInfo
Constants ¶
const ( Epsilon float64 = 1e-8 Padding float64 = 0.005 )
Variables ¶
This section is empty.
Functions ¶
func BoxBoxContain ¶ added in v1.4.0
BoxBoxContain returns true if a fully contains b (b is fully inside of the bounds of a).
func BoxBoxOverlap ¶ added in v1.4.0
BoxBoxOverlap checks whether a and b overlap.
If h is not nil, the function fills it with for box b:
- Normal: Collision surface normal for box b
- Data: the penetration depth for box b (overlap distance)
This method can behave poorly for moving objects.
For continuous motion, BoxBoxSweep1() of BoxBoxSweep2() should be used instead.
func BoxBoxSweep1 ¶ added in v1.4.0
BoxBoxSweep1 Returns true if collision occurs during movement. Fills hit info h for dynamicB if not nil.
func BoxBoxSweep2 ¶ added in v1.4.0
BoxBoxSweep2 Returns true if collision occurs during movement. Fills hit info h for b if not nil.
func BoxCircleOverlap ¶ added in v1.4.0
BoxCircleOverlap checks whether box and circle overlap.
If h is not nil, the function fills it with:
- Normal: the surface normal of box
- Data: penetration depth (distance to move the box)
To resolve the overlap:
newBoxPos = box.Pos.Add(hit.Normal.Neg().Scale(hit.Data))
func BoxCircleSweep2 ¶ added in v1.4.0
BoxCircleSweep2 checks for collision between a moving AABB and a moving Circle.
Returns true if collision occurs during movement, false otherwise.
func BoxOrientedBoxOverlap ¶ added in v1.4.6
BoxOrientedBoxOverlap tests if an AABB and OBB are currently intersecting. For moving objects, use BoxOrientedBoxSweep2 to prevent tunneling.
func BoxOrientedBoxSweep2 ¶ added in v1.4.6
BoxOrientedBoxSweep2 tests if a moving AABB and moving OBB intersect during their motion. Uses swept volume testing to prevent tunneling for fast-moving objects.
func BoxPointOverlap ¶ added in v1.4.0
BoxPointOverlap returns true if the point is in the box, false otherwise. If h is not nil, the function fills it with for point:
- Normal: Collision surface normal for box
- Data: the penetration depth for point
func BoxSegmentOverlap ¶ added in v1.4.0
BoxSegmentOverlap returns true if they intersect, false otherwise.
Params:
- box - Bounding box to check
- start - Ray segment origin/start position
- delta - Ray segment move/displacement vector
- padding - Padding added to the radius of the bounding box
- h - Contact info for segment. Filled when argument isn't nil and a collision occurs
func BoxSegmentSweep1 ¶ added in v1.4.0
BoxSegmentSweep1 sweep a moving box against a static line segment.
If h is not nil and a collision is detected, it will be populated with:
- Normal: Collision surface normal for the box
- Data: Normalized time of impact (0.0 to 1.0) along the movement path
func BoxSegmentsSweep1Indexed ¶ added in v1.4.3
BoxSegmentsSweep1Indexed returns the index of the colliding segment, or -1 if no collision was detected.
Performs a sweep test of an box against a slice of segments.
To determine the earliest point of impact along a movement vector, It iterates through the provided segments and finds the collision that occurs at the minimum time value. If h is not nil and a collision is detected, it will be populated with:
- Normal: Collision surface normal for the box
- Data: Normalized time of impact (0.0 to 1.0) along the movement path
func CircleCircleSweep2 ¶ added in v1.4.7
CircleCircleSweep2 checks for collision between two moving circles to prevent tunneling.
Returns true if collision occurs during movement or if they are already overlapping.
If h is not nil and a collision is detected, it will be populated with:
- Normal: Collision surface normal for c2
- Data: Normalized time of impact (0.0 to 1.0) along the movement path
func LineCircleOverlap ¶ added in v1.4.0
LineCircleOverlap checks if the infinite line defined by the given raySeg intersects with a circle. Return true if the infinite line passes through the circle This function treats 'raySeg' as a line extending infinitely in both directions
Parameters:
- raySeg: Defines the trajectory (slope and position) of the infinite line.
- c: The Circle struct to test against.
- result: If non-nil and an intersection occurs, this is populated with the two intersection points along the infinite line.
func RayTilemapDDA ¶ added in v1.4.0
func RayTilemapDDA(pos, dir v.Vec, mag float64, tileMap [][]uint8, cellSize float64, hit *Hit) (bool, image.Point)
RayTilemapDDA performs the DDA (Digital Differential Analysis) algorithm to find intersections with a tile map
youtube.com/watch?v=NbSee-XM7WA
Parameters:
- pos: Starting position of the ray
- dir: Direction unit vector of the ray (should be normalized)
- mag: Maximum distance the ray can travel
- tileMap: 2D grid of cells where any non-zero value represents a wall/obstacle
- cellSize: Size of each tile in the grid
- hit: Optional pointer to Hit struct (can be nil)
Returns:
- bool: True if a collision occurred
- image.Point: The grid coordinates of the wall that was hit (0,0 if no hit)
func SegmentCircleOverlap ¶ added in v1.3.3
SegmentCircleOverlap returns the intersection points of a Segment and a Circle.
If the returned slice is nil, there is no intersection.
The length can be 1 or 2. It can be queried with the len() method.
Types ¶
type AABB ¶
type AABB struct {
Pos v.Vec // Center position of the box.
Half v.Vec // Half-extents (half dimensions) from the center.
}
AABB represents an Axis-Aligned Bounding Box.
type Circle ¶ added in v1.1.0
type Circle struct {
Pos v.Vec // Center position of the circle.
Radius float64 // The radius of the circle.
}
Circle represents a circular bounding volume.
type Hit ¶ added in v1.5.0
type Hit struct {
// The normal vector of the hit.
Normal v.Vec
// 1. The time (0.0 to 1.0) along the movement path for moving objects.
//
// 2. Penetration depth for overlap tests
Data float64
}
Hit holds the information about a collision or contact event.
type OBB ¶ added in v1.4.6
type OBB struct {
Pos v.Vec // Center position of the box.
Half v.Vec // Half-extents (half dimensions) from the center.
Angle float64 // Rotation angle from center (Pos). Unit in radians. (Clockwise)
}
OBB represents an Oriented Bounding Box
type Segment ¶
Segment shape with A and B points.
func NewSegment ¶ added in v1.3.2
NewSegment returns new Segment
type TileCollider ¶ added in v1.1.0
type TileCollider struct {
Collisions []TileHitInfo // List of collisions from last check
CellSize image.Point // Width and height of tiles
TileMap [][]uint8 // 2D grid of tile IDs
NonSolidTileIDs []uint8 // Sets the ID of non-solid tiles. Defaults to 0.
}
TileCollider handles collision detection between AABB and [][]uint8 2D tilemap
func NewTileCollider ¶ added in v1.1.0
func NewTileCollider(tileMap [][]uint8, tileWidth, tileHeight int) *TileCollider
NewTileCollider creates a new tile collider with the given tilemap and tile dimensions
func (*TileCollider) Collide ¶ added in v1.1.0
func (c *TileCollider) Collide(box AABB, delta v.Vec, onCollide TileCollisionCallback) v.Vec
Collide checks for collisions when a moving aabb and returns the allowed movement
type TileCollisionCallback ¶ added in v1.1.0
type TileCollisionCallback func([]TileHitInfo, float64, float64)
TileCollisionCallback is called when collisions occur, receiving collision info and final movement
Source Files
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- box_box_contain.go
- box_box_overlap.go
- box_box_sweep1.go
- box_box_sweep2.go
- box_circle_overlap.go
- box_circle_sweep2.go
- box_orientedbox_overlap.go
- box_orientedbox_sweep2.go
- box_point_overlap.go
- box_seg_overlap.go
- box_seg_sweep1.go
- box_segs_sweep1_indexed.go
- box_tilemap_sweep.go
- circle_circle_sweep2.go
- coll.go
- line_circle_overlap.go
- ray_tilemap_dda.go
- seg_circle_overlap.go
- shapes.go
Directories
