Geometric constraints
Constraints are the parametric half of ForceCanvas: rules that hold between pieces of geometry and survive dragging. Select geometry on the canvas and the constraints that apply to that selection appear in the toolbar.
How constraints behave
- Contextual. A constraint button only appears once your selection can accept it: select two lines and Parallel appears, select a point and a line and Point on Line appears.
- Solved, not snapped. Applying a constraint re-solves the whole sketch so every rule holds at once, rather than nudging geometry into place.
- Live while dragging. Drag any point and the solver keeps every constraint satisfied as the geometry moves.
- Reviewable. The Constraints panel on the right edge lists everything applied. Hover to highlight it on the canvas, toggle it off temporarily, or delete it.
The Constraints panel
The actual panel, embedded live and populated with a small example sketch: a locked origin point, a horizontal base, and a perpendicular post. Each row shows the constraint type, the geometry it applies to, and a switch to disable it without deleting it. The toggles are inert here because there's no canvas behind the page.
Point constraints
Select one or more points, plus a line where noted.
Select 2 or more points. Merges them so they move together as one location.
Select points and one line. Holds each point anywhere on that line's infinite extension.
Select points and one line. Like Point on Line, but confines the point between the two endpoints.
Select points and one line. Pins each point to the exact center of that line.
Select 2 or more points. Forces them to share a Y coordinate.
Select 2 or more points. Forces them to share an X coordinate.
Select a single point. Pins it to its current coordinates so nothing can move it, useful as a ground reference.
Line constraints
Select one or more lines.
Select 2 or more lines. Holds them at the same direction.
Select 2 or more lines. Holds them at 90° to each other.
Select 2 or more lines. Forces them to share a length without fixing what that length is.
Select one or more lines. Forces each to lie flat along the X axis.
Select one or more lines. Forces each to stand along the Y axis.
Circle constraints
Circles are reference geometry. They help you lay out a sketch but never carry force.
Select points and one circle. Holds each point on the circumference.
Select lines and one circle. Holds each line touching the circle at exactly one point.
Select 2 or more circles. Forces them to share a center point.
Select 2 or more circles. Forces them to share a radius.
Dimensions
Dimensions are driving constraints that carry a number. Type a new value and the geometry moves to match.
Applies a length, point-to-point distance, point-to-line distance, radius, diameter, or angle depending on what you select.
Under, fully, and over-constrained
Geometry is colored by how well-defined it is: under-constrained geometry still has freedom to move, fully constrained geometry is locked down, and over-constrained geometry has conflicting or redundant rules that will fight each other. The exact colors are on the Canvas Legend page. This is a separate idea from the beam stability overlay, which is about whether the structure can be solved for forces.