User:Voludu2/Segment and node IDs

2,499 bytes added, 5 months ago
removed redundant item stating that there is a node connected to any free/unattached end of a segment
When you edit, you are often creating an and deleting segments and nodes, even when you don't realize it.
If you take a moment to select the segments and nodes and look at their IDs in the left pane, you can see what is happening.
* Every segment has a unique segment ID.
* There is a node at the end of each segment. Each node has a unique segment ID.
** If that node forms the junction between two or more segments, editors often call it a "junction node"
** If that node is only attached to one segment, editors often call it an "end node"
* If you select a node and move it, all attached segments ends will move with it.
* If a node has no segments attached to it, it will be deleted.
* If you select a segment and move one of its ends, it will leave the node (junction or end) behind
* If you select a segment, move one of its ends, and attach that end to a junction of 2 or more segments, or to the unattached end of another segment, that segment will now be attached to the node at the new location
* If you select a segment, move one of its ends, and leave that end unattached in the new location, a new node will be created at the unattached end of the segment.
* If you merge two segments by deleting the node between them, or by using the bridge button, the node and both segments are deleted and replaced by a new segment with a new segment ID
* If you cut a segment into two segments, the original segment is deleted. Two new segments are created and one new node joining them
Here is what happened during an actual editing session.
[[File{{User:Voludu2/AI4|image=Segment_node_ids1.png|image-width=600|width=400|image-top=-50|thumbheight=300|caption=Every segment is attached to two nodes - one node at each end of the segment.]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids2.png|image-width=600|width=400|image-top=-50|thumbheight=300|caption=At the junction, two segments are connected to the same node. There is exatly one node at a junction.]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids3.png|image-width=600|width=400|image-top=-50|thumbheight=300|caption=When a segment is highlighted and one end is dragged away from a node, A a new node is automatically created on the segment that was just moved.]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids2.png|image-width=600|thumbwidth=400|image-top=-50|height=300|caption=When a node is dragged and connected to another node, the "stationary" node (the one that didn't get dragged) is retained. The node that was moved is deleted.]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids4.png|image-width=600|width=400|image-top=-50|thumbheight=300|caption=When a segment is cut by connecting another segment dragging a node to a point somewhere in the middle,two new segments are created. The dragged node from the end of the segment used for cutting becomes the node for the new junction]]. When a segment is cut by dragging the segment end (without the formerly-attached node), a new node is created at the cut point.|annotation=}}[[File{{User:Voludu2/AI4|image=Segment_node_ids5.png|image-width=600|width=400|image-top=-50|thumbheight=300|caption=A segment is disconnected from the junction and gains a new node at the end]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids6.png|image-width=600|width=400|image-top=-50|thumbheight=300|caption=Another segment is disconnected from the junction]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids7.png|image-width=600|thumbwidth=400|image-top=-50|height=300|caption=Two segments are joined. The stationary node from the stationary segment is retained as the junction node and the node from the moving end of the other segment is deleted]]}}[[File{{User:Voludu2/AI4|image=Segment_node_ids8.png|thumbimage-width=600|width=400|image-top=-50|height=300|caption=If you select the junction of 2 segments and drag it to another node, both segments will have their ends dragged along with the junction]][[File|annotation=}}{{User:Voludu2/AI4|image=Segment_node_ids9.png|thumbimage-width=600|width=400|image-top=-50|height=300|caption=All the segments are now joined at one junction. The stationary node is retained for the junction node. The node that was moved is deleted.]]|annotation=}}{{User:Voludu2/AI4|image=Segment node ids10.png|image-width=600|width=400|image-top=-50|height=300|caption=Replacing a junction with a roundabout preserves the segment IDs, but the junction node ID is lost. There is a new node where each of the segments joins the new roundabout|annotation=}}
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