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Class: Manifold ​

A manifold for two touching convex shapes. Manifolds are created in evaluate method of Contact subclasses.

Supported manifold types are e_faceA or e_faceB for clip point versus plane with radius and e_circles point versus point with radius.

We store contacts in this way so that position correction can account for movement, which is critical for continuous physics. All contact scenarios must be expressed in one of these types. This structure is stored across time steps, so we keep it small.

Constructors ​

Constructor ​

new Manifold(): Manifold

Returns ​

Manifold

Properties ​

localNormal ​

localNormal: Vec2Value

Usage depends on manifold type:

  • circles: not used
  • faceA: the normal on polygonA
  • faceB: the normal on polygonB

localPoint ​

localPoint: Vec2Value

Usage depends on manifold type:

  • circles: the local center of circleA
  • faceA: the center of faceA
  • faceB: the center of faceB

pointCount ​

pointCount: number = 0

The number of manifold points

points ​

points: ManifoldPoint[]

The points of contact

type ​

type: ManifoldType

clipSegmentToLine() ​

static clipSegmentToLine: (vOut, vIn, normal, offset, vertexIndexA) => number

Clips the segment vIn against the half-plane normal.v <= offset, into vOut, and returns the point count.

Contact ids follow one convention, written as if the reference face were on shape A (the collider swaps them afterwards when it is on B): a point that is an incident vertex k lying on the reference face f carries (f, e_face, k, e_vertex), and a point produced here, the incident edge cut by the side plane at reference vertex j, carries (j, e_vertex, edge, e_face). The two kinds differ in their feature types and two points of one kind differ in their index, so the points of a manifold never share an id; Contact.update relies on that to carry warm-start impulses to the right point.

Parameters ​

vOut ​

ClipVertex[]

vIn ​

ClipVertex[]

normal ​

Vec2Value

offset ​

number

vertexIndexA ​

number

the reference vertex whose side plane this is

Returns ​

number

ClipVertex ​

static ClipVertex: typeof ClipVertex

getPointStates() ​

static getPointStates: (state1, state2, manifold1, manifold2) => void

Compute the point states given two manifolds. The states pertain to the transition from manifold1 to manifold2. So state1 is either persist or remove while state2 is either add or persist.

Parameters ​

state1 ​

PointState[]

state2 ​

PointState[]

manifold1 ​

Manifold

manifold2 ​

Manifold

Returns ​

void

PointState ​

static PointState: typeof PointState

Methods ​

getWorldManifold() ​

getWorldManifold(wm, xfA, radiusA, xfB, radiusB): WorldManifold

Evaluate the manifold with supplied transforms. This assumes modest motion from the original state. This does not change the point count, impulses, etc. The radii must come from the shapes that generated the manifold.

Parameters ​

wm ​

WorldManifold

xfA ​

TransformValue

radiusA ​

number

xfB ​

TransformValue

radiusB ​

number

Returns ​

WorldManifold

recycle() ​

recycle(): void

Returns ​

void

set() ​

set(that): void

Parameters ​

that ​

Manifold

Returns ​

void