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Common Entities

About 3 min

Common Entities

The most commonly used entity types in everyday development.

LineEnt - Line

const { LineEnt, Engine } = vjcad;

// Create a line
const line = new LineEnt([0, 0], [100, 100]);  // Start point, end point
line.setDefaults();
line.color = 1;  // Red
Engine.addEntities(line);

Properties:

  • startPoint / endPoint - Start/end point (Point2D)
  • Length - Length (read-only)
  • color - Color
  • layer - Layer
  • lineType - Linetype
  • lineTypeScale - Linetype scale

CircleEnt - Circle

const { CircleEnt, Engine } = vjcad;

// Create a circle
const circle = new CircleEnt([50, 50], 30);  // Center, radius
circle.setDefaults();
circle.color = 3;  // Green
Engine.addEntities(circle);

Properties:

  • center - Center (Point2D)
  • radius - Radius
  • area - Area (read-only)
  • circumference - Circumference (read-only)

ArcEnt - Arc

const { ArcEnt, Point2D, Engine } = vjcad;

// Method 1: Center + radius + angles (radians)
const arc = new ArcEnt([50, 50], 30, 0, Math.PI / 2);  // 0° to 90°
arc.setDefaults();
Engine.addEntities(arc);

// Method 2: Three-point arc
const arc2 = new ArcEnt();
arc2.initBy3Pt(new Point2D(0, 0), new Point2D(50, 30), new Point2D(100, 0));
arc2.setDefaults();
Engine.addEntities(arc2);

Properties:

  • center - Center
  • radius - Radius
  • startAngle / endAngle - Start/end angle (radians)
  • startPoint / endPoint - Start/end point (read-only)
  • midPoint - Mid point (read-only)
  • length - Arc length (read-only)
  • totalAngle - Central angle (read-only)
  • isClockwise - Whether clockwise (read-only)

Methods:

  • initBy3Pt(p1, p2, p3) - Create arc through three points

PolylineEnt - Polyline

const { PolylineEnt, BulgePoints, BulgePoint, Engine } = vjcad;

// Method 1: Using setPoints (recommended)
const pline = new PolylineEnt();
pline.setPoints([
    [0, 0],
    [100, 0],
    [100, 60],
    [0, 60]
]);
pline.isClosed = true;  // Close
pline.setDefaults();
Engine.addEntities(pline);

// Method 2: Chained addPoint
const pline2 = new PolylineEnt();
pline2.addPoint([0, 0])
      .addPoint([50, 0], 0.5)  // Arc segment with bulge
      .addPoint([100, 0]);
pline2.setDefaults();
Engine.addEntities(pline2);

// Method 3: Polyline with arc segments
const pline3 = new PolylineEnt();
pline3.setPoints([
    [0, 0],              // Straight segment
    [[50, 0], 0.5],      // Arc segment (bulge 0.5, counter-clockwise)
    [100, 0],
    [[100, 50], -0.5]    // Arc segment (negative bulge, clockwise)
]);
pline3.setDefaults();
Engine.addEntities(pline3);

Bulge explanation:

  • 0 - Straight line segment
  • 1 - Semicircular arc (counter-clockwise)
  • -1 - Semicircular arc (clockwise)
  • bulge = tan(centralAngle/4)

Properties:

  • bulgePoints - Vertex collection (BulgePoints)
  • isClosed - Whether closed
  • length - Total length (read-only)
  • area - Area (when closed, read-only)
  • isCCW - Whether counter-clockwise (read-only)
  • globalWidth - Global width

Methods:

  • setPoints(points) - Set points in batch
  • addPoint([x,y], bulge?) - Add point (supports chaining)
  • addPoints(points) - Append points in batch
  • getPoints() - Get all vertex coordinates
  • getPointsWithBulge() - Get vertices with bulge info
  • getSubEnts() - Get sub-entities (line segments and arcs)

TextEnt - Single-Line Text

const { TextEnt, Engine } = vjcad;

const text = new TextEnt();
text.insertionPoint = [0, 100];  // Insertion point
text.text = "Hello WebCAD";      // Text content
text.height = 10;                // Text height
text.rotation = 0;               // Rotation angle (radians)
text.textAlignment = 5;          // Alignment (see below)
text.setDefaults();
text.color = 2;
Engine.addEntities(text);

Text alignment (textAlignment):

7=TopLeft     8=TopCenter     9=TopRight
4=MidLeft     5=MidCenter     6=MidRight
1=Left        2=Center        3=Right (baseline alignment)

Special characters:

  • %%d → ° (degree)
  • %%c → Ø (diameter)
  • %%p → ± (plus-minus)

Properties:

  • insertionPoint - Insertion point
  • text - Text content
  • height - Text height
  • rotation - Rotation angle (radians)
  • textAlignment - Alignment (1-9)
  • widthFactor - Width factor
  • obliqueAngle - Oblique angle (radians)

MTextEnt - Multi-Line Text

const { MTextEnt, Engine } = vjcad;

const mtext = new MTextEnt();
mtext.insertionPoint = [0, 100];
mtext.text = "First line\nSecond line\nThird line";  // \n for line break
mtext.height = 8;
mtext.maxWidth = 80;  // Auto wrap when exceeding width
mtext.setDefaults();
Engine.addEntities(mtext);

MText format codes (using contents property):

// Color
mtext.contents = "{\\C1;Red}{\\C2;Yellow}{\\C3;Green}";

// Font size
mtext.contents = "{\\H1.5x;Large} Normal {\\H0.7x;Small}";

// Style
mtext.contents = "{\\LUnderline} {\\OOverline} {\\KStrikethrough}";

// Line break
mtext.contents = "First line\\PSecond line";

Format code quick reference:

CodeFunction
\Cn;Color (1=Red 2=Yellow 3=Green 4=Cyan 5=Blue 6=Magenta 7=White)
\L / \lUnderline on/off
\O / \oOverline on/off
\K / \kStrikethrough on/off
\Hn.nx;Relative height (e.g. \H1.5x;)
\Wn;Width factor
\PLine break
{}Format grouping

Properties:

  • insertionPoint - Insertion point
  • text - Text content (supports \n line breaks)
  • contents - Native MText format content
  • height - Text height
  • maxWidth - Maximum width (auto wrap)
  • textAttachment - Attachment point position (1-9)
  • rotation - Rotation angle
  • rowSpcFac - Line spacing factor
  • showBorder - Whether to show border
  • backgroundFill - Whether to enable background
  • backgroundFillColor - Background color
  • backgroundScaleFactor - Background scale factor

Less Common Entities

EllipseEnt - Ellipse

const { EllipseEnt, Engine } = vjcad;

const ellipse = new EllipseEnt();
ellipse.center = [50, 50];
ellipse.majorAxis = [40, 0];   // Major axis vector
ellipse.radiusRatio = 0.5;     // Minor/major axis ratio
ellipse.setDefaults();
Engine.addEntities(ellipse);

SplineEnt - Spline Curve

const { SplineEnt, Point2D, Engine } = vjcad;

const spline = new SplineEnt();
spline.setFitPoints([
    new Point2D(0, 0),
    new Point2D(50, 100),
    new Point2D(100, 50),
    new Point2D(150, 100)
]);
spline.setDefaults();
Engine.addEntities(spline);

RayEnt / XlineEnt - Ray / Construction Line

const { RayEnt, XlineEnt, Engine } = vjcad;

// Ray (extends infinitely from start point in one direction)
const ray = new RayEnt([0, 0], [1, 1]);  // Start point, direction
ray.setDefaults();
Engine.addEntities(ray);

// Construction line (extends infinitely in both directions)
const xline = new XlineEnt([50, 50], [1, 0]);  // Through point, direction
xline.setDefaults();
Engine.addEntities(xline);

DotEnt - Point

const { DotEnt, Engine } = vjcad;

const dot = new DotEnt([50, 50]);
dot.setDefaults();
Engine.addEntities(dot);

SolidEnt - Solid Fill

const { SolidEnt, Engine } = vjcad;

// Triangle fill
const solid = new SolidEnt([0, 0], [100, 0], [50, 80]);
solid.setDefaults();
solid.color = 1;
Engine.addEntities(solid);

// Quadrilateral fill
const solid2 = new SolidEnt([0, 0], [100, 0], [0, 80], [100, 80]);
solid2.setDefaults();
Engine.addEntities(solid2);

Common Properties

All entities support the following properties:

PropertyDescriptionExample
colorColor index1=Red 2=Yellow 3=Green 4=Cyan 5=Blue 6=Magenta 7=White, 256=ByLayer
layerLayer name"LayerA"
lineTypeLinetype name"CONTINUOUS", "HIDDEN", "CENTER"
lineTypeScaleLinetype scale1.0
lineWeightLine weight15 (0.15mm), -1 ByLayer

Common Methods

MethodDescription
setDefaults()Apply system default properties (must be called before setting other properties)
boundingBox()Get bounding box
clone()Create a copy
move(from, to)Move
rotate(center, angle)Rotate (radians)
scale(center, factor)Scale
mirror(p1, p2)Mirror