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Primitive Geometries

Primitive geometries are the building blocks of sketches — lines, arcs, and curves. They follow a "pen" model: each command starts from where the last one ended.

circle​

circle() takes a diameter (not radius):

import { sketch } from 'fluidcad/core';
import { circle } from 'fluidcad/core';

sketch("xy", () => {
    circle(50)
    circle([30, 20], 40)
})

Circles

line​

sketch("xy", () => {
    line([0, 0], [100, 0])     // from [0,0] to [100,0]
    line([100, 50])            // continues to [100, 50]
    line([0, 0])               // back to start, closing the shape
})

Directional lines​

import { sketch } from 'fluidcad/core';
import { line, vLine, hLine } from 'fluidcad/core';

sketch("xy", () => {
    line([0, 0], [50, 0])
    vLine(40)
    hLine(-50)
    line([0, 0])
})

Directional lines

  • hLine(distance) — horizontal line (positive = right, negative = left)
  • vLine(distance) — vertical line (positive = up, negative = down)
  • aLine(angle, distance) — line at an angle (degrees) for a given distance
sketch("xy", () => {
    line([0, 0], [50, 0])
    aLine(60, 40)              // 60° angle, 40 units long
    line([0, 0])
})

arc​

sketch("xy", () => {
    arc(50, 0, 90)             // radius 50, from 0° to 90°
})

Tangent arcs​

tArc() draws an arc that is tangent to the previous line or arc — the arc starts in the same direction the pen is currently pointing (shown by the orange arrow in the viewport). This creates smooth, continuous curves:

import { sketch } from 'fluidcad/core';
import { vLine, tArc } from 'fluidcad/core';

sketch("front", () => {
    vLine(100)
    tArc(50, 180)
    tArc(80, -270)
})

Tangent arcs

bezier​

Draws bezier curves through control points:

sketch("xy", () => {
    bezier([0, 0], [50, 100], [100, 0])   // quadratic bezier (1 control point)
})

The last point is the endpoint. Points in between are control points:

  • 2 points = straight line
  • 3 points = quadratic bezier (1 control point)
  • 4 points = cubic bezier (2 control points)
Interactive mode

Call bezier() with no arguments to enter interactive mode. Click in the viewport to place control points with a live preview of the curve. Use Ctrl+click to drag existing points, and Escape to undo.