How parametric intent maps to the Recipe

In classic CAD, design intent lives in three places at once: sketch relations (this line is tangent to that arc), dimensions and equations (this width is twice that height), and feature order (cut after shell). Solid Vibes keeps all three ideas, but distributes them differently. Knowing where each one lives tells you how to build models that survive change.

The three layers

Intent by construction

Most intent is enforced by writing a dependent value as an expression of its driver. The relationship is then part of the definition, so it cannot be violated.

Expressions can use + - * / ^ %, parentheses, parameter names, min max abs sqrt round floor ceil sin cos tan asin acos atan atan2 (trig in degrees) and pi. Nothing else is allowed, so every formula is deterministic and safe.

Intent by checking

Some rules depend on the whole shape and cannot be built into a formula. For these, a design intent entry holds a boolean check expression that is re-evaluated after every rebuild, producing a green or red chip.

Available measurements: bbox_x(), bbox_y(), bbox_z(), volume(), min_wall().

Intent kinds are centered, symmetric, equal, min, max, fixed, aligned and custom. Each can reference parameters or steps (refs) for highlighting, and records whether you or the agent wrote it.

Create them by speaking in rules: "Always keep the lid the same width as the box", "Never go thinner than 1.6 mm".

Sketch constraints

Sketches come in two flavours, and both are parametric:

• Constrained sketches (sketch mode) are geometry plus constraints and dimensions, solved by the kernel's constraint solver on every build. Dimensions can be parameter formulas, so a parameter change re-solves the sketch; the editor shows what is still free (blue), fully defined (black) or over-defined (red), and names conflicting constraints. See Sketching with constraints.
• Shape-based sketches (a rectangle of width w, a circle of radius r, a path through formula points) are defined directly by their values and formulas. Sloppy sketch produces these, and records the constraints it inferred as intent metadata. Open one in sketch mode (or press Constrain in Sloppy sketch) to turn it into a constrained sketch — sizes and formulas are kept.

Either way, when a relationship spans several features (holes centered on a plate that is extruded later), express it with parameters and formulas, and record it as a design intent rule.

Feature order still matters

The Recipe is ordered, and later steps depend on earlier ones.

• Fillets before a shell behave differently from fillets after it.
• A hole placed on a face refers to a face that must exist at that point in the Recipe.
• A boolean uses a named tool body that must be created first.

You can move steps. If a move breaks a dependency, the step turns red with a plain-language explanation, and the agent offers a repair as a ghost preview. See A step turned red after I changed a parameter.

Suppression instead of deletion

To explore, suppress a step instead of deleting it. The step stays in the Recipe, marked off. The agent works the same way: it never deletes history. This keeps alternatives, Compare and replays meaningful.

Designing for change

A checklist for models that survive their first redesign:

1. Name the drivers (board_width, wall, fit_clearance) before anything that depends on them.
2. Derive everything else with formulas. If you type a number twice, it should be a parameter.
3. Group parameters (Fit, Mounting, Appearance) and set slider ranges to the plausible range.
4. Write the rules that must hold as design intent. Keep the list short and meaningful.
5. Select by meaning, not by position, so edits survive.
6. Order steps so risky features (fillets) come after the geometry they depend on, and cosmetic ones last.
7. Try an alternative before a large change.
8. Stress-test it. Drag every driving slider to both ends of its range and watch for red steps or chips.

Try it

Audit this piece for robustness to change. List every hard-coded number that should be a parameter, every relationship that should be a formula, and three design intent rules worth adding. Do not change anything yet.

Then apply the suggestions you agree with, and run the slider stress test.