Class AcDbArc

Represents an arc entity in AutoCAD.

An arc is a 2D geometric object defined by its center point, radius, start angle, and end angle. Arcs are portions of circles that can be used to create curved line segments in drawings. The arc is always drawn in the plane defined by its normal vector.

Example

// Create a 90-degree arc from 0 to π/2 radians
const arc = new AcDbArc(
  new AcGePoint3d(0, 0, 0),
  10,
  0,
  Math.PI / 2
);

// Access arc properties
console.log(`Center: ${arc.center}`);
console.log(`Radius: ${arc.radius}`);
console.log(`Start angle: ${arc.startAngle}`);
console.log(`End angle: ${arc.endAngle}`);

Hierarchy (View Summary)

Constructors

constructor

Accessors

attrs center closed color database endAngle endPoint geometricExtents layer lineStyle lineType linetypeScale lineWeight objectId ownerId radius rgbColor startAngle startPoint transparency type visibility

Methods

close draw getAttr getAttrWithoutException getLayerColor setAttr subGetGripPoints subGetOsnapPoints transformBy triggerModifiedEvent

Constructors

constructor

  • new AcDbArc(
        center: AcGeVector3dLike,
        radius: number,
        startAngle: number,
        endAngle: number,
    ): AcDbArc

  • Creates a new arc entity.

    This constructor creates an arc using the specified center point, radius, start angle, and end angle. The center point must be in World Coordinate System (WCS) coordinates. Angles are specified in radians.

    Parameters

    • center: AcGeVector3dLike

      The center point of the arc in WCS coordinates

    • radius: number

      The radius of the arc (must be positive)

    • startAngle: number

      The starting angle in radians (0 to 2π)

    • endAngle: number

      The ending angle in radians (0 to 2π)

    Returns AcDbArc

    Example

    // Create a quarter circle arc (0 to 90 degrees)
    const quarterArc = new AcDbArc(
      new AcGePoint3d(0, 0, 0),
      15,
      0,
      Math.PI / 2
    );

    // Create a semicircle arc (0 to 180 degrees)
    const semicircle = new AcDbArc(
      new AcGePoint3d(10, 20, 0),
      25,
      0,
      Math.PI
    );

Accessors

attrs

center

closed

  • get closed(): boolean

  • Gets whether this arc is closed.

    An arc is considered closed if the start and end angles are the same (forming a complete circle).

    Returns boolean

    True if the arc is closed (forms a complete circle), false otherwise

color

database

  • get database(): AcDbDatabase

  • Gets the database in which this object is resident.

    When an object isn't added to a database, this property returns the current working database. After it is added to a database, it will be set automatically. You should never set this value manually.

    Returns AcDbDatabase

    The database this object belongs to

    Example

    const db = obj.database;
  • set database(db: AcDbDatabase): void

  • Sets the database for this object.

    This is typically set automatically when the object is added to a database. Manual setting should be avoided unless you know what you're doing.

    Parameters

    Returns void

    Example

    obj.database = myDatabase;

endAngle

  • get endAngle(): number

  • Gets the end angle of this arc.

    Returns number

    The end angle in radians

    Example

    const endAngle = arc.endAngle;
    console.log(`Arc end angle: ${endAngle} radians (${endAngle * 180 / Math.PI} degrees)`);
  • set endAngle(value: number): void

  • Sets the end angle of this arc.

    Parameters

    • value: number

      The new end angle in radians (0 to 2π)

    Returns void

    Example

    arc.endAngle = Math.PI; // 180 degrees

endPoint

  • get endPoint(): AcGePoint3d

  • Gets the end point of this arc.

    The end point is calculated based on the center, radius, and end angle.

    Returns AcGePoint3d

    The end point as a 3D point

    Example

    const endPoint = arc.endPoint;
    console.log(`Arc end point: ${endPoint.x}, ${endPoint.y}, ${endPoint.z}`);

geometricExtents

  • get geometricExtents(): AcGeBox3d

  • Gets the geometric extents (bounding box) of this arc.

    Returns AcGeBox3d

    The bounding box that encompasses the entire arc

    Example

    const extents = arc.geometricExtents;
    console.log(`Arc bounds: ${extents.minPoint} to ${extents.maxPoint}`);

layer

  • get layer(): string

  • Gets the name of the layer referenced by this entity.

    Returns string

    The layer name

    Example

    const layerName = entity.layer;
  • set layer(value: string): void

  • Sets the name of the layer for this entity.

    Parameters

    • value: string

      The new layer name

    Returns void

    Example

    entity.layer = 'MyLayer';

ProtectedlineStyle

  • get lineStyle(): AcGiLineStyle

  • Gets the line style for this entity.

    This method returns the line style based on the entity's linetype and other properties.

    Returns AcGiLineStyle

    The line style object

    Example

    const lineStyle = entity.lineStyle;

lineType

  • get lineType(): string

  • Gets the name of the line type referenced by this entity.

    Returns string

    The linetype name

    Example

    const lineType = entity.lineType;
  • set lineType(value: string): void

  • Sets the name of the line type for this entity.

    Parameters

    • value: string

      The new linetype name

    Returns void

    Example

    entity.lineType = 'DASHED';

linetypeScale

  • get linetypeScale(): number

  • Gets the line type scale factor of this entity.

    When an entity is first instantiated, its line type scale is initialized to an invalid value. When the entity is added to the database, if a linetype scale has not been specified for the entity, it is set to the database's current line type scale value.

    Returns number

    The linetype scale factor

    Example

    const scale = entity.linetypeScale;
  • set linetypeScale(value: number): void

  • Sets the line type scale factor for this entity.

    Parameters

    • value: number

      The new linetype scale factor

    Returns void

    Example

    entity.linetypeScale = 2.0;

lineWeight

  • get lineWeight(): number

  • Gets the line weight used by this entity.

    Returns number

    The line weight value

    Example

    const weight = entity.lineWeight;
  • set lineWeight(value: number): void

  • Sets the line weight for this entity.

    Parameters

    • value: number

      The new line weight value

    Returns void

    Example

    entity.lineWeight = 2;

objectId

  • get objectId(): string

  • Gets the object ID.

    AutoCAD uses 64-bit integers to represent handles, which exceed the maximum integer value of JavaScript. Therefore, strings are used to represent object handles.

    Returns string

    The object ID as a string

    Example

    const id = obj.objectId;
    console.log(`Object ID: ${id}`);
  • set objectId(value: string): void

  • Sets the object ID.

    Parameters

    • value: string

      The new object ID

    Returns void

    Example

    obj.objectId = 'new-object-id';

ownerId

  • get ownerId(): string

  • Gets the object ID of the owner of this object.

    Returns string

    The owner object ID

    Example

    const ownerId = obj.ownerId;
  • set ownerId(value: string): void

  • Sets the object ID of the owner of this object.

    Parameters

    • value: string

      The new owner object ID

    Returns void

    Example

    obj.ownerId = 'parent-object-id';

radius

  • get radius(): number

  • Gets the radius of this arc.

    Returns number

    The radius value

    Example

    const radius = arc.radius;
    console.log(`Arc radius: ${radius}`);
  • set radius(value: number): void

  • Sets the radius of this arc.

    Parameters

    • value: number

      The new radius value (must be positive)

    Returns void

    Example

    arc.radius = 25;

rgbColor

  • get rgbColor(): number

  • Gets the RGB color of this entity after converting color index.

    This method handles the conversion of color indices (including ByLayer and ByBlock) to actual RGB colors. It resolves layer colors and block colors as needed.

    Returns number

    The RGB color value as a number

    Example

    const rgbColor = entity.rgbColor;
    console.log(`RGB: ${rgbColor.toString(16)}`);

startAngle

  • get startAngle(): number

  • Gets the start angle of this arc.

    Returns number

    The start angle in radians

    Example

    const startAngle = arc.startAngle;
    console.log(`Arc start angle: ${startAngle} radians (${startAngle * 180 / Math.PI} degrees)`);
  • set startAngle(value: number): void

  • Sets the start angle of this arc.

    Parameters

    • value: number

      The new start angle in radians (0 to 2π)

    Returns void

    Example

    arc.startAngle = Math.PI / 4; // 45 degrees

startPoint

  • get startPoint(): AcGePoint3d

  • Gets the start point of this arc.

    The start point is calculated based on the center, radius, and start angle.

    Returns AcGePoint3d

    The start point as a 3D point

    Example

    const startPoint = arc.startPoint;
    console.log(`Arc start point: ${startPoint.x}, ${startPoint.y}, ${startPoint.z}`);

transparency

  • get transparency(): number

  • Gets the transparency level of this entity.

    Returns number

    The transparency value (0-1, where 0 is opaque and 1 is fully transparent)

    Example

    const transparency = entity.transparency;
  • set transparency(value: number): void

  • Sets the transparency level of this entity.

    Parameters

    • value: number

      The transparency value (0-1, where 0 is opaque and 1 is fully transparent)

    Returns void

    Example

    entity.transparency = 0.5; // 50% transparent

type

  • get type(): string

  • Gets the type name of this entity.

    This method returns the entity type by removing the "AcDb" prefix from the constructor name.

    Returns string

    The entity type name

    Example

    const entity = new AcDbLine();
    console.log(entity.type); // "Line"

visibility

  • get visibility(): boolean

  • Gets whether this entity is visible.

    Returns boolean

    True if the entity is visible, false otherwise

    Example

    const isVisible = entity.visibility;
  • set visibility(value: boolean): void

  • Sets whether this entity is visible.

    Parameters

    • value: boolean

      True to make the entity visible, false to hide it

    Returns void

    Example

    entity.visibility = false; // Hide the entity

Methods

close

  • close(): void

  • Closes the object.

    All changes made to the object since it was opened are committed to the database, and a "closed" notification is sent. This method can be overridden by subclasses to provide specific cleanup behavior.

    Returns void

    Example

    obj.close();

draw

getAttr

  • getAttr(attrName: string): any

  • Gets the value of the specified attribute.

    This method will throw an exception if the specified attribute doesn't exist. Use getAttrWithoutException() if you want to handle missing attributes gracefully.

    Parameters

    • attrName: string

      The name of the attribute to retrieve

    Returns any

    The value of the specified attribute

    Throws

    When the specified attribute doesn't exist

    Example

    try {
      const value = obj.getAttr('objectId');
    } catch (error) {
      console.error('Attribute not found');
    }

getAttrWithoutException

  • getAttrWithoutException(attrName: string): any

  • Gets the value of the specified attribute without throwing an exception.

    This method returns undefined if the specified attribute doesn't exist, making it safer for optional attributes.

    Parameters

    • attrName: string

      The name of the attribute to retrieve

    Returns any

    The value of the specified attribute, or undefined if it doesn't exist

    Example

    const value = obj.getAttrWithoutException('optionalAttribute');
    if (value !== undefined) {
      // Use the value
    }

ProtectedgetLayerColor

  • getLayerColor(): null | AcCmColor

  • Gets the color of the layer this entity belongs to.

    This method retrieves the color from the layer table for the layer this entity belongs to.

    Returns null | AcCmColor

    The layer color, or undefined if the layer doesn't exist

    Example

    const layerColor = entity.getLayerColor();

setAttr

subGetGripPoints

  • subGetGripPoints(): AcGePoint3d[]

  • Gets the grip points for this arc.

    Grip points are control points that can be used to modify the arc. For an arc, the grip points are the center point, start point, and end point.

    Returns AcGePoint3d[]

    Array of grip points (center, start point, end point)

    Example

    const gripPoints = arc.subGetGripPoints();
    // gripPoints contains: [center, startPoint, endPoint]

subGetOsnapPoints

  • subGetOsnapPoints(
        osnapMode: AcDbOsnapMode,
        gsSelectionMark: number,
        pickPoint: AcGePoint3d,
        lastPoint: AcGePoint3d,
        snapPoints: AcGePoint3d[],
    ): void

  • Gets the object snap points for this entity.

    Object snap points are the points that can be used for precise positioning when drawing or editing. This method should be overridden by subclasses to provide entity-specific snap points.

    Parameters

    Returns void

    Example

    const snapPoints: AcGePoint3d[] = [];
    entity.subGetOsnapPoints(AcDbOsnapMode.Endpoint, 0, pickPoint, lastPoint, snapPoints);

transformBy

  • transformBy(matrix: AcGeMatrix3d): AcDbArc

  • Transforms this arc by the specified matrix.

    This method applies a geometric transformation to the arc, updating the center point, radius, and angles according to the transformation matrix.

    Parameters

    Returns AcDbArc

    This arc after transformation

    Example

    const translationMatrix = AcGeMatrix3d.translation(10, 0, 0);
    arc.transformBy(translationMatrix);
    // Arc is now translated 10 units in the X direction

triggerModifiedEvent

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