Sketch Blocks and Constraints

KCL sketch blocks define 2D geometry and the relationships that control it. Start a block on a base plane or supported face, add sketch geometry inside the braces, then apply constraints to express design intent.

Inside a sketch block, the solver module is automatically in scope. Call line, arc, circle, coincident, and other solver functions without a solver:: prefix.

var values are initial guesses

A value introduced with var is a coordinate or size that the solver may change. It is an initial guess, not a fixed dimension. Initial guesses must be numeric literals, with a unit where applicable:

Put identifiers and expressions in constraints when they must drive the solved result. For example, use horizontalDistance([edge.start, edge.end]) == width rather than end = [var width, var 0mm].

Fully constrain the sketch

A fully constrained sketch has no unintended degrees of freedom. Use geometric constraints such as coincident, horizontal, vertical, parallel, perpendicular, equalLength, tangent, and symmetric to describe relationships. Use dimensional constraints such as distance, horizontalDistance, verticalDistance, angle, radius, and diameter for driving values.

Anchor the profile once, then constrain the rest of the geometry relative to that frame. Repeatedly fixing absolute points makes sketches harder to edit and can over-constrain them. An under-constrained sketch can move in unintended ways; an over-constrained sketch contains redundant or conflicting relationships.

See the constraint reference for the full API and the sketching guide for the point-and-click workflow.

Create a region from a closed profile

Most solid features consume a region created from a closed sketch boundary.

For one closed segment, such as a circle, pass that segment by itself. Omit intersectionIndex and direction; they are unnecessary for one loop and are intended to disambiguate a boundary traced from multiple segments.

For a boundary traced from multiple intersecting segments, pass the first two segments. Use intersectionIndex only when they intersect more than once, and use direction = CW when the default counterclockwise trace selects the wrong boundary.

If segment tracing cannot identify the intended boundary, make the boundary unambiguous by passing an adjacent segment pair and setting direction or intersectionIndex when needed. For new code, prefer correcting the boundary selection instead of falling back to a coordinate inside the region.

Control arc direction

An arc sweeps counterclockwise from its start point to its end point by default. If it takes the long or opposite path, set direction = CW. Changing the direction is clearer than swapping endpoints and then repairing every dependent constraint.