Geometry (CAD)

The MagFEM drawing is parametric, in the style of Onshape: you sketch freely and then lock the shape with constraints (horizontal, tangent, coincident…) and dimensions (distances, radii, angles). Dimensions accept units and expressions with variables, so changing a variable redraws the whole model. The constraint solver is PlaneGCS, the same one used by FreeCAD.

Drawing tools

Tool	Key	Use
Select	S or Esc	click selects, Shift adds; drag to move
Measure (ruler)	U	two clicks measure a distance; does not change the drawing
Line / polyline	L	each click continues the polyline; ends when closing on an existing point, on a double-click or with Esc
Construction line	Shift+L	helper line: guides the drawing but does not form regions
Rectangle	R	two opposite corners (created as a group, with H/V)
Center rectangle	Shift+R	center and one corner (symmetric about the center)
Circle	C	center and a point on the edge
Three-point arc	A	start, end and a point on the arc
Center arc	Shift+A	center, start and end (the mouse movement picks the direction)
Point	P	free point (handy as a dimension reference)

Buttons with a small arrow group variants (line/construction, rectangle/center, three-point/center arc); the button shows the last variant used.

Snapping

While drawing, the cursor snaps, in this order, to:

1. existing points (end points, centers, the Origin): the new point becomes that same point;

2. line midpoints: adds a “midpoint” constraint;

3. curves: adds “point on curve”;

4. the x and y axes (r and z in axisymmetric problems): adds a vertical or horizontal constraint to the Origin.

For lines, the second point also infers horizontal or vertical when it is nearly aligned, and snaps to where that direction crosses the nearest curve. All these constraints show up in the tree (Geometry › Constraints) and can be deleted.

The Origin

Clicking the origin creates a point of its own with a Coincident constraint to the Origin. To free the part, delete that constraint. Older drawings where a curve uses the Origin itself show Detach from origin in the properties panel.

Constraints

Select the entities and click the constraint button (or press its key).

Constraint	Key	Entities
Coincident	I	two points, or a point and a curve (point on)
Horizontal / Vertical	H / V	a line, or two points
Parallel / Perpendicular		two lines
Tangent	T	a line and an arc/circle, or two arcs/circles
Equal	E	two lines (length) or two arcs/circles (radius)
Midpoint	M	a point and a line
Symmetric		two points and an axis (line)
Concentric		two arcs/circles
Fix		pins points at their current position

The color shows the state: blue still has degrees of freedom, black (white in the dark theme) is fully defined. The status bar shows how many degrees of freedom remain. A constraint that conflicts with the others is refused, with a message in the status bar.

Dimensions and variables

With the Dimension tool (D), click an entity (or two) and then where you want the text; type the value.

• A line or two points give a distance; the text position picks the aligned, horizontal or vertical distance.

• A circle gives the diameter; an arc gives the radius; two lines give an angle; a point and a line give the point-to-line distance.

• The value accepts a number (in the project unit), a number with a unit (2 cm, 0.5 in) or an expression with variables (Ds/2 - g).

Variables live under Geometry › Variables (+ creates one). Double-clicking a dimension edits its value.

Editing

Action	Key	Description
Trim	X	click a piece of a curve to remove it, up to the nearest intersections. At an end it shortens the curve; in the middle it splits it in two; a cut circle becomes an arc; a curve with no crossings is deleted
Offset	O	parallel copy at a distance (associative: follows the original)
Mirror		reflects the selection about a line or axis
Linear / circular pattern		copies in a grid or around a center
Move / rotate	G	translates and rotates the selection by typed values
Group / Ungroup	Ctrl+G / Ctrl+Shift+G	a group is selected and moved as one part; double-click enters the group to edit an entity
Construction	Q	toggles a curve between normal and construction
Delete	Del	deletes the selection
Fit	F	frames the drawing
Undo / Redo	Ctrl+Z / Ctrl+Shift+Z (or Ctrl+Y)

Offset, mirror and patterns are associative: the copy follows the original when it changes, and the distance or the number of copies stays editable in the properties.

Box selection

As in CAD programs, dragging a box to the right selects what lies entirely inside it; dragging to the left selects everything it touches.

Planar and axisymmetric

In the Problem and libraries drawer, choose the problem type and the length unit:

• Planar: x and y; set the depth (length along z), used for flux linkage, energy and force.

• Axisymmetric: r (horizontal) and z (vertical), with the symmetry axis at r = 0. Only the r ≥ 0 half-plane counts; it is highlighted and MagFEM warns when something is drawn at r < 0.

Importing geometry

Import accepts DXF and SVG: curves are added to the drawing and coincident points are merged so regions close. See also Files, import and export.