Snap & point sharing
Snap and point sharing both deal with “this point goes on that thing.” They look similar in the UI, but they have different consequences. Mixing them up is the most common source of “why did my shapes drift?” bugs.
Snap = same coordinate
Section titled “Snap = same coordinate”Snapping moves your cursor (or a vertex you’re dragging) to land on an existing target. The result is two distinct points that happen to share coordinates.
Move the original target later and your snapped point doesn’t follow. They were never linked.
This is what you want when you’re sketching: precise alignment, no hidden coupling.
Sharing = same identity
Section titled “Sharing = same identity”A shared point is one object referenced by several shapes. Move it once, every shape that holds the reference moves with it.
You create shared points by holding Alt while clicking, or by dragging a vertex onto an existing one in segment-editing mode.
This is what you want for boundaries that should never separate — two adjoining lane edges, two polygon corners that need to stay welded, the end of one path and the start of another.
Why distinguish
Section titled “Why distinguish”If two shape edges that should be the same are actually two snapped points, drag one of them, export to OpenDRIVE, and the road network opens up at that vertex. The simulator may interpret the gap as a discontinuity, or smear over it depending on the tool.
Lane Left/Right neighbours that share a boundary always use shared points internally — that’s not optional and not user-controlled. For arbitrary shapes (Linestring, Polygon, Path), the choice is up to you.
Visual cues
Section titled “Visual cues”- A snap target shows a single highlighted handle and pulls the cursor.
- A shared point renders as a doubled handle in segment-editing mode.