Circle from 3 Points

The Circle from 3 Points panel (VIEW3D_PT_circumcenter) builds a circle that passes through three selected mesh vertices, using their circumcenter as the centre. Useful for reconstructing column drums, apses, well rings, and any radial feature when only a portion of the arc has been surveyed.

This page is the parameter and operator reference for the panel.

Source: utils/circumcenter_tool.py. Sidebar tab: 3DSC. Default state: collapsed (DEFAULT_CLOSED). Visible only when the active object is a mesh.

Required state

The panel walks the user through three prerequisites and refuses to expose the operator until all are satisfied:

  1. The active mesh must be in Edit Mode (the panel offers a shortcut button to enter it).

  2. Exactly three vertices must be selected. The panel reports the current selection count and offers a shortcut to switch to vertex select mode.

  3. The three vertices must not be collinear (validated by the operator at execution time).

Parameters

Once the selection is valid, the panel exposes:

Segments

Number of segments used to build the circle mesh. Range [3, 128], default 32.

Circle Color

RGBA colour used both for the operator preview and, when Create as new object is enabled, for the resulting object’s viewport display. Default (0.0, 0.8, 1.0, 1.0) (cyan).

Create as new object

When enabled (default), the circle is generated as a new object in the scene. When disabled, the circle is added to the active object’s mesh as additional geometry.

Operator

mesh.apply_circumcenter — Create Circle

Reads the three selected vertices, computes the circumcenter and the radius, and creates the circle according to the current parameters.

Typical workflow

  1. Select the mesh containing the partial arc.

  2. Enter Edit Mode.

  3. Switch to Vertex select mode.

  4. Select exactly three vertices on the surveyed arc.

  5. Tune Segments and Circle Color if needed.

  6. Press Create Circle.

Remember

The circle is mathematically defined by the three vertices — accuracy depends entirely on how well the input points represent the intended geometry. Pick vertices spread along the arc (not clustered) for a stable fit.