Parameters and expressions

Every dimension and feature input is a model parameter (d1, d2, …). User parameters are ones you add yourself, with a unit, an expression and an optional comment. Change them in Change Parameters (parameters.change). The timeline rebuilds from the first feature that uses them.

Expressions are unit-aware: 2 * width + 5 mm, angle / 2, sqrt(area), 1 in + 3 mm, using + - * / ^, parentheses, sin cos tan asin acos atan atan2 sqrt abs min max floor ceil round mod trunc and unit conversion. A length where an angle is expected (or the other way round) is an error, not a silent conversion. Cycles are reported with their path (a → b → a), renaming a parameter updates every expression, dimension and feature input that uses it, and a parameter in use can’t be deleted (the error lists its users).

The design’s units (Document Settings in the browser: mm, cm, m, in or ft) set how a bare number typed into a feature is read. In an inch design 2 means 2 in. Changing the units never moves existing geometry.

Parameters export to and import from CSV or JSON (parameters.export, parameters.import). Configurations (config.*) keep a table of rows, each with its own parameter values and suppressed features, switched with config.activate.