Constraint creation

Author geometric and dimensional constraints on the ACS canvas by selecting vertices and edges, then choosing an action from the floating bar.

Overview

The ACS parametric sketcher lets you author geometric constraints directly on the canvas by selecting vertices and edges and then picking an action from a floating bar. This page covers the authoring workflow — how to select geometry and create constraints. For managing existing constraints (editing values, removing, resolving conflicts), see Parametric sketcher.

Select tool

Constraint creation requires the Select tool — the arrow cursor in the top-left tool palette of the ACS canvas. Click the arrow icon or press Escape to enter Select mode.

Selecting geometry

One-step selection

Clicking a vertex or edge immediately selects it — there is no prior hover or focus step. The selection is visible at once; vertex handles (the small dots on the outline) appear as soon as the outline is hovered or any item is selected.

Plain click — single selection

A plain click (no modifier key) selects one item:

• Click a vertex (dot handle on the outline or on a freeform void ring) — selects that vertex.
• Click an edge (the line or arc segment between two vertices, on the outline or a freeform void) — selects that edge.

A plain click also resets any previous single-selection, replacing it with the newly clicked item.

Shift-click — additive multi-selection

Hold Shift while clicking to extend the selection without replacing it:

• Shift-click a vertex — adds it to the accumulated selection.
• Shift-click an edge — adds the edge.

Constraint actions appear in the floating bar only when the accumulated selection forms a valid combination (see Selection-to-action table below). Items accumulate until you click the canvas background to clear or click a constraint button to apply.

Clearing the selection

Click anywhere on the canvas background (not on an outline vertex or edge) to clear both single and multi-selection.

Constraint action bar

When a valid selection is assembled — a single edge or vertex, or a multi-selection — the constraint action bar appears at the top-centre of the canvas. It shows one button per available constraint type for the current selection.

Click a button to apply the constraint. The bar closes, the constraint is saved immediately, and the sketch status chip updates.

Properties panel

The constraint multi-select you are building on the canvas operates independently of the properties panel. Assembling a multi-selection or hovering over the action bar does not scroll or highlight the properties panel.

Once you click an action bar button and the constraint is created, it immediately appears in the Constraint List Panel — accessible from the Constraints tab in the left sidebar. Open that tab after creating a constraint to edit its locked value, see its state badge, or remove it. See Parametric sketcher for full panel details.

Selection-to-action table

A single arc edge offers no action — Horizontal and Vertical apply only to straight edges (there is no axis to align an arc to).

:::note Coincident requires vertices from two different rings. On sections with a freeform (polygon) void — a box girder, for example — the outline and each void are sibling rings, so selecting one vertex on each offers Coincident, exactly as in GCS. :::

:::note Freeform void rings are constrainable; parametric hollows are not. The vertices and edges of a freeform polygon void carry the same selection handles as the outline and participate in every constraint above. The circular void of a parametric hollow section (a hollow circle authored from its outer/inner diameters) is the one exception: its geometry is rebuilt from the diameter drivers whenever a diameter is edited, so a constraint there would be silently overwritten — those void rings offer no selection handles and can never be constrained. :::

System-generated constraints

Some constraints are created automatically by ACS when you perform an action in another panel — they never require a canvas selection. These constraints appear in the Constraint List Panel alongside user-authored ones, but they are not accessible through the selection-to-action workflow above.

Tie-corner constraints

When you place a cell tie from the Reinforcement panel, ACS automatically creates a set of tie-corner constraints that align each corner of the tie path with the nearest longitudinal bar position in that cell. This means the tie hugs the bar group as you move bars — the tie corners track the bars, not the other way around.

Tie-corner constraints:

• Appear in the Constraint List Panel labelled as “Tie corner” with the associated cell and corner index.
• Cannot be created by selecting vertices or edges on the canvas — the selection-to-action table above applies only to user-authored constraints.
• Are removed automatically when the cell tie they belong to is deleted.
• Can be individually removed from the Constraint List Panel if you want a corner to float freely; removing one turns that corner from a tracked position into an ordinary free vertex.

Constraint health indicator

The outline stroke reflects the sketch’s constraint health and updates live as constraints are added or removed:

Typical workflow

1. Select the Select tool (arrow) in the tool palette.
2. Click the first vertex or edge to select it.
3. Shift-click the second (and optionally third) item.
4. The constraint action bar appears. Click the desired constraint button.
5. The constraint is saved. The outline stroke and status chip update immediately.

Tips

• You don’t always need a multi-selection: a single straight edge offers Horizontal / Vertical, and a single vertex offers Fix — select just the one item and the action bar appears.
• To select an edge, click near its midpoint — clicking close to a vertex usually picks the vertex instead.
• After applying a constraint the selection is cleared. Shift-clicking accumulates a fresh set for the next constraint.
• The status chip in the canvas header is the fastest way to confirm the sketch is well-constrained before running an analysis.
• If the outline turns red after adding a constraint, a conflict dialog opens — see Parametric sketcher to resolve it.

Keyboard shortcuts

Next steps

• Parametric sketcher — persisted locks, vertex dragging with constraint enforcement, and the Constraint List Panel.
• Section geometry — drawing the outline before applying constraints.
• Canvas navigation — pan, zoom, and fit controls.