Interface Edge

An Edge of a RigidBody has a start and finish Vertex and belongs to a particular RigidBody. Vertex location is defined in body coordinates of the associated RigidBody. An Edge knows which side is outside or inside the RigidBody; the method getNormalBody returns a normal vector that points to the outside.

Edges are ordered in a RigidBody. For a given Edge, the start Vertex must be the same as the finish Vertex of the previous Edge of the RigidBody.

Terminology

A normal vector is a perpendicular to an Edge, see https://en.wikipedia.org/wiki/Normal_(geometry).

A unit normal is a normal vector with length 1. Here 'normal vector' usually also implies that it is a unit normal vector.

interface Edge {
    addPath(context): void;
    chordError(): number;
    distanceToEdge(edge): number;
    distanceToLine(p_body): number;
    distanceToPoint(p_body): number;
    findVertexContact(v, p_body, distTol): null | RigidBodyCollision;
    forgetPosition(): void;
    getBody(): RigidBody;
    getBottomBody(): number;
    getCentroidBody(): Vector;
    getCentroidRadius(): number;
    getCentroidWorld(): Vector;
    getCurvature(p_body): number;
    getDecoratedVertexes(): Vertex[];
    getIndex(): number;
    getLeftBody(): number;
    getNormalBody(p_body): Vector;
    getPointOnEdge(p_body): Vector[];
    getRightBody(): number;
    getTopBody(): number;
    getVertex1(): Vertex;
    getVertex2(): Vertex;
    highlight(): void;
    improveAccuracyEdge(rbc, edge): void;
    intersection(p1_body, p2_body): null | Vector[];
    intersectionPossible(edge, swellage): boolean;
    isStraight(): boolean;
    maxDistanceTo(p_body): number;
    pointOffset(p_body, length): Vector;
    setCentroidRadius(value): void;
    setVertex2(vertex): void;
    testCollisionEdge(collisions, edge, time): void;
    toStringShort(): string;
}

Hierarchy (view full)

Implemented by

Methods

addPath chordError distanceToEdge distanceToLine distanceToPoint findVertexContact forgetPosition getBody getBottomBody getCentroidBody getCentroidRadius getCentroidWorld getCurvature getDecoratedVertexes getIndex getLeftBody getNormalBody getPointOnEdge getRightBody getTopBody getVertex1 getVertex2 highlight improveAccuracyEdge intersection intersectionPossible isStraight maxDistanceTo pointOffset setCentroidRadius setVertex2 testCollisionEdge toStringShort

Methods

addPath

  • addPath(context): void

  • Add this Edge to the currently open path of the JavaScript canvas context for drawing the Edge. The Edge should be drawn in local body coordinates.

    Parameters

    • context: CanvasRenderingContext2D

      the JavaScript canvas context to draw this Edge into

    Returns void

chordError

  • chordError(): number

  • Returns the maximum distance between this Edge and any chord between Vertexes on this Edge (including decorated mid-point Vertexes). A chord is the straight line between two adjacent Vertexes.

    Here is a picture of a curved Edge, the chord between two Vertexes, V1, V2, and the chord error is the maximum distance between the chord and curved Edge.

    Note that having more decorated mid-point Vertexes results in a smaller chord error, because the chords are closer to the curve.

    See Vertex for more about decorated mid-point Vertexes

    Returns number

    the maximum distance between this Edge and a chord between any Vertexes on this Edge

distanceToEdge

  • distanceToEdge(edge): number

  • Returns smallest distance between this Edge and the given Edge. Returns NaN in cases where the calculation can't be done. One of the Edges must be curved.

    TO DO distanceToEdge is not used currently... delete it? or use it in places like CircleStraight.testCollision and CircleCircle.testCollision?

    Parameters

    • edge: Edge

      the Edge to measure distance to

    Returns number

    smallest distance between this Edge and the given Edge, or NaN when the calculation cannot be done

    Throws

    if both Edges are StraightEdges.

distanceToLine

  • distanceToLine(p_body): number

  • Returns distance from the given point (in body coordinates) to the extended line of this Edge, where the extensions continue beyond the endpoints of this Edge. For a CircularEdge the extended line is taken to be the full circle. Positive distance means the point is outside of this Edge, negative means inside.

    Parameters

    • p_body: Vector

      the point to find distance from, in body coords

    Returns number

    distance from the given point to the extended line of this Edge

distanceToPoint

  • distanceToPoint(p_body): number

  • Returns signed distance of the given point (in body coordinates) to this Edge along a line that is normal to this Edge, or infinity if beyond an endpoint of this Edge. Distance is positive if it is on the side of the line that the normal points towards, otherwise negative.

    Parameters

    • p_body: Vector

      the point to find distance from, in body coords

    Returns number

    signed distance from the given point to this Edge (positive if point is on side the normal points towards) or infinity if beyond the endpoint of this Edge

findVertexContact

  • findVertexContact(v, p_body, distTol): null | RigidBodyCollision

  • Returns a RigidBodyCollision representing the contact point if the given Vertex is close to this Edge. Closeness is specified by the given distance tolerance. Note that this does not consider velocity tests for a contact. If the point does not lie along any normal to this Edge, then it is not close; this occurs when the point is past the endpoints of this Edge.

    If the point is near, then the returned RigidBodyCollision will have the following information set:

    • body is set to the RigidBody of the Vertex
    • normalBody is set to the RigidBody of this Edge
    • impact point is set to the nearest point on this Edge, in world coords
    • distance is set to the distance of Vertex from this Edge; negative distance means penetration into this Edge.
    • normal is set to the unit normal vector at the nearest point on this Edge, in world coords
    • r2 is based on current position of this Edge's RigidBody

    Additionally, if this Edge is curved, the following are also set: ballNormal, radius2, u2.

    Parameters

    • v: Vertex

      the Vertex of interest on other-body

    • p_body: Vector

      the body coordinate position of the Vertex in body coords of this Edge's body (normalBody)

    • distTol: number

      the distance tolerance; distance to Vertex must be smaller than this to be considered close enough.

    Returns null | RigidBodyCollision

    a RigidBodyCollision representing the contact point, or null if not close enough.

forgetPosition

getBody

getBottomBody

  • getBottomBody(): number

  • Returns the bottom-most position of this Edge, in body coordinates.

    Returns number

    bottom-most position of this Edge, in body coordinates

getCentroidBody

  • getCentroidBody(): Vector

  • Returns the center of the circle to use for proximity testing, in body coordinates. A circle centered at this centroid with radius getCentroidRadius() should encompass this Edge. See getCentroidRadius and getCentroidWorld.

    Returns Vector

    the center of the circle to use for proximity testing, in body coordinates

getCentroidRadius

getCentroidWorld

  • getCentroidWorld(): Vector

  • Returns the center of the circle to use for proximity testing, in world coordinates. A circle centered at this point with radius getCentroidRadius() should encompass this Edge. See getCentroidRadius and getCentroidBody.

    Returns Vector

    the center of the circle to use for proximity testing, in world coordinates

getCurvature

  • getCurvature(p_body): number

  • Returns radius of curvature at the given point on this Edge. Radius of curvature is the radius of a circle that would give equivalent curvature at a given point on an Edge. Negative curvature means the Edge is concave at that point.

    For a circle, every point on the circle has the same center and radius of curvature. But for any other curve (an oval for instance), each point on the edge can have a different center and radius of curvature.

    Parameters

    • p_body: Vector

      the point on this Edge, in body coordinates

    Returns number

    the radius of curvature; negative means concave; returns positive infinity if this is a straight edge

    Throws

    if the point is not close to this Edge

getDecoratedVertexes

getIndex

  • getIndex(): number

  • Returns the index of this Edge in the RigidBody's list of Edges

    Returns number

    the index of this Edge in the RigidBody's list of Edges.

getLeftBody

  • getLeftBody(): number

  • Returns the left-most position of this Edge, in body coordinates.

    Returns number

    left-most position of this Edge, in body coordinates

getNormalBody

  • getNormalBody(p_body): Vector

  • Returns unit normal vector in body coordinates, at the given body coordinates point. Normal points outwards from the RigidBody. TO DO what if the point is not on this Edge?

    Parameters

    • p_body: Vector

      the point on this Edge in body coordinates

    Returns Vector

    the outwards pointing unit normal vector at the given point, in body coordinates

getPointOnEdge

  • getPointOnEdge(p_body): Vector[]

  • Finds the nearest point on this Edge to the given point, returns that nearest point and the unit normal vector there. Returns null if the given point lies beyond the end point of this Edge, meaning that there is no perpendicular line to this Edge passing thru the given point.

    Parameters

    • p_body: Vector

      a point near this Edge, in body coordinates

    Returns Vector[]

    a pair of Vectors: the nearest point on this Edge, and the unit normal vector at that point both in body coords; or null if there is no nearest point on this Edge.

getRightBody

  • getRightBody(): number

  • Returns the right-most position of this Edge, in body coordinates.

    Returns number

    right-most position of this Edge, in body coordinates

getTopBody

  • getTopBody(): number

  • Returns the top-most position of this Edge, in body coordinates.

    Returns number

    top-most position of this Edge, in body coordinates

getVertex1

  • getVertex1(): Vertex

  • The start Vertex of this Edge. Should match the finish Vertex of the previous Edge in the RigidBody.

    Returns Vertex

    the start Vertex of this Edge

getVertex2

highlight

improveAccuracyEdge

  • improveAccuracyEdge(rbc, edge): void

  • Updates the EdgeEdgeCollision to have more accurate information based on current positions and velocities of the RigidBodys.

    Parameters

    Returns void

intersection

  • intersection(p1_body, p2_body): null | Vector[]

  • Returns points on this Edge intersecting the straight line segment between the two given points (in body coordinates), or null if there is no intersection. There can be more than one point of intersection.

    Parameters

    • p1_body: Vector

      point 1 in body coords

    • p2_body: Vector

      point 2 in body coords

    Returns null | Vector[]

    array of intersection points, in body coords, or null if no intersection.

intersectionPossible

  • intersectionPossible(edge, swellage): boolean

  • Rough proximity test that returns true if an intersection is possible between this Edge and the specified Edge. This is intended to do a quick rough test to eliminate obvious cases where no intersection is possible. Swellage is a fudge factor which is added to the max radius of the Edges, to make the test easier to succeed.

    Parameters

    • edge: Edge

      the other Edge

    • swellage: number

      a fudge factor which is added to the max radius of the Edges

    Returns boolean

    whether an intersection between the Edges is possible

isStraight

  • isStraight(): boolean

  • Whether this Edge is a straight line.

    Returns boolean

    true if this Edge is a straight line

maxDistanceTo

  • maxDistanceTo(p_body): number

  • Returns the maximum distance from the given point (in body coordinates) to any point on this Edge.

    Parameters

    • p_body: Vector

      a point in body coordinates

    Returns number

    the maximum distance from the given point (in body coordinates) to any point on this Edge

pointOffset

  • pointOffset(p_body, length): Vector

  • Returns the point offset in the direction of this Edge's normal. The normal is taken at the point on this Edge that is closest to the given point. The point is given and returned in body coordinates. Note that the returned point might be closer to this Edge when the starting point is on the inside of the RigidBody, because the normal points outwards.

    Parameters

    • p_body: Vector

      the point near this Edge, in body coordinates

    • length: number

      the distance to move the point

    Returns Vector

    the point offset in the direction of this Edge's normal, in body coordinates

setCentroidRadius

setVertex2

  • setVertex2(vertex): void

  • Sets the finish Vertex of this Edge. Should match the start Vertex of the next Edge in the RigidBody.

    Parameters

    • vertex: Vertex

      the finish Vertex of this Edge

    Returns void

testCollisionEdge

  • testCollisionEdge(collisions, edge, time): void

  • If there is a collision between this Edge and the given Edge, adds a RigidBodyCollision to the list. This ignores collisions with Vertexes.

    Parameters

    • collisions: RigidBodyCollision[]

      list of collisions to add to

    • edge: Edge

      the other Edge

    • time: number

      current simulation time

    Returns void

toStringShort

  • toStringShort(): string

  • Returns a minimal string representation of this object, usually giving just identity information like the class name and name of the object.

    For an object whose main purpose is to represent another Printable object, it is recommended to include the result of calling toStringShort on that other object. For example, calling toStringShort() on a DisplayShape might return something like this:

    DisplayShape{polygon:Polygon{'chain3'}}

    Returns string

    a minimal string representation of this object.

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