SplineEdit

Remarks

[docs/plan/31 § T8]'s viewport editing, on the gizmo and SnapContext that already exist. A control point is a position and nothing else, so dragging one is what IGizmoTarget already does — which is why this is a target and a command rather than a mode.

⚠ Tangent handles are selectable in their own right, and they have to be. A tangent is where the curve leaves a point, and the only way to author a corner is to move one of them without the other — so a handle set that held only positions could express a smooth road and nothing else.

⚠ The undo record is the whole point list. A stroke on a heightfield records a rect because a terrain is megabytes; a spline is a hundred points and about three kilobytes, so the machinery that makes a rect worth having buys nothing here and costs a class of bug — an edit that inserts or removes a point changes every index after it, which a per-point delta would have to reason about and a whole-list snapshot does not.

Fields and properties (6)

• public SplineAsset? Asset

  Which spline is being edited.

• public SnapContext? Snapping

  What snapping applies to a drag, or none.

• public float PickRadius

  How close a pick has to be to a handle, in metres.

• public float HandleScale

  How far a tangent handle sits from its point, as a fraction of the tangent.

• public IReadOnlyCollection<SplineHandle> Selection

  Which handles are selected.

• public bool HasSelection

  Whether anything is selected.

Methods (10)

• public Vector3? PositionOf(SplineHandle handle)

  Where a handle is, in world space.

• public SplineHandle? Pick(Vector3 at, bool add = false)

  Selects the handle nearest a point, if one is close enough.

• public void Deselect()

  Deselects everything.

• public void Begin()

  Takes a snapshot, so the drag that follows becomes one undo entry.

• public void Move(Vector3 delta, bool mirror = true)

  Moves every selected handle by a world-space delta.

• public int Append(Vector3 at)

  Appends a control point at the end of the path and selects it.

• public int InsertOn(Vector3 near)

  Inserts a control point on the curve nearest a place, without changing its shape.

• public int Delete()

  Removes every selected control point.

• public SplineCommand? Commit()

  Ends the drag, as one entry for the undo stack.

• public void Cancel()

  Abandons the drag, putting the points back.

Used by (2)

• SplineCommandVixen.Editor.SceneView
• SplineEditTestsVixen.Editor.SceneView.Tests