Circle tool — Cadivari Knowledge Base

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Recommended test

This sequence checks the complete first circle iteration.

Press C, click a centre point, move outward, and click again to create a circle.
Confirm the live label reports both diameter and radius before the second click.
Press V, select the circle, then drag its centre handle and radius handle.
Enter exact values for CX, CY, and R. Change D and confirm R updates to half that value.
Undo and redo the edits, then delete and undo the deletion.

01 · CREATE

Draw from centre to radius

Activate Circle from the left tool rail or press C. Click once to place the centre, move the pointer outward to preview the size, then click again to commit the circle.

The centre remains visible

After the first click, a fixed circular marker identifies the exact centre while the offset pointer leaves the geometry coordinate unobstructed. A zero-radius circle is never added.

The preview label displays diameter and radius in millimetres. This is the same click–preview–click pattern used by Line, so the next geometry point always remains clear.

02 · DIRECT EDITING

Move the centre or change the radius

Press V and select a circle by its outline. The outline has a comfortable invisible selection band, but the circle interior does not capture clicks; concentric circles therefore remain independently selectable. Two distinct handles appear:

+Dashed centre handle moves the circle without changing its radius

○Solid handle on the right edge changes the radius while the centre stays fixed

Each completed drag creates one history entry. Press Esc before release to discard an active handle edit.

03 · PRECISION

Enter exact values

The Properties panel exposes the circle’s canonical centre and size in millimetres.

CXCentre position, horizontal

CYCentre position, vertical

RRadius; must be positive

DDiameter; always twice the radius

Press Enter or leave a field to commit. R and D are synchronized: changing either one updates the other. Invalid or zero-size results are rejected.

04 · ALIGNMENT

Reuse existing geometry

While Snap is enabled, the circle’s centre and radius point can lock to the configured grid, which uses 10 mm spacing by default, or to line and arc endpoints and rectangle corners. Geometry snaps use a comfortable screen-space distance and show a named green marker before the point is accepted.

Deliberate first-iteration boundary

Existing circles are not yet snap targets. Centre and quadrant snapping will be introduced as part of a broader snap expansion so every tool receives the same predictable behaviour.

3D PROFILES

Use circles to divide a sketch into regions

A circle crossed by ordinary sketch lines or an unmirrored spline produces individually selectable areas in 3D > Push/Pull. Two crossing diameter lines create four quadrants. Overlapping circles create a shared lens and two crescents, and circular arcs can close regions together with lines. A contained circle can still define a hole or a separately selectable disk. Try an S-shaped spline crossing the circle twice to create two regions with a shared curved boundary; see spline region extrusion.

Click one region to extrude it, or Ctrl-click several regions in the same sketch and choose Extrude selected. New body, Join and Cut use the same workflow. The circle stays editable, and changes rebuild the stored region when its boundary connections remain intact. If the region is split, merged or opened, restore its boundaries or select the intended area for a new extrusion. See the circle-and-arc test and current limits.

Use Trim (X) to remove a circular section between supported crossings. The remainder becomes one or two ordinary arcs with the original radius. This changes the sketch geometry; existing features whose boundary references change may need to be recreated.

REFERENCE

Controls

CActivate Circle

VActivate Select

EscCancel a draft or active handle edit

DeleteDelete selected circle

Ctrl + ZUndo creation, deletion, or edit

Ctrl + YRedo

IMPLEMENTATION NOTE

Document model

A circle is stored as a mathematical centre point and positive radius. The model uses canonical millimetres in Y-up document space and is independent from the SVG renderer.

{
  "kind": "circle",
  "center": { "x": 80, "y": 60 },
  "radius": 35
}

Diameter is calculated from the radius rather than stored separately, so those two values cannot drift apart. This representation can later feed SVG/DXF export, contour validation, and circular CAM paths.

CURRENT SCOPE

Exact circular contours and annular regions are available

Inside and Outside circular CAM contours with exact radius compensation
Two exact G2/G3 semicircles per contour depth pass through 3D, animation, preflight, and export
Selectable circular pocket regions, including concentric annular recesses with a preserved centre island
Circle centre and quadrant points as snapping targets remain planned
Tangent, midpoint, and intersection snapping remain planned
Three-point circle construction remains planned
Dragging a circle directly by its outline remains planned

Use an Inside contour for a through bore, or a shallow annular pocket for a gasket seat, decorative ring, or rosette channel.