Hello,
Can someone please help me to understand the topology builder attributes : right_edge and left_adge with some concrete examples and illustrations ?
I've tried to understand and apply just from the description in the transformer docomentation but couldn't
Thank you very much in advance
Best answer by jdh
Consider the following simple grid. The _edge_id 3 is highlighted with the starting node at the center.
If you travel in the direction of the line, when you get to the to_node, there are two other edges, 1, and 7. The right edge is the segment you would be on if you turned right.
If on the other hand, you travel in the reverse direction along edge 3, from the outside to the center, at the from_node there are 3 options: 2, 5, 6, Turning right would have you on edge 6.
So the right_edge is 1 and the left edge is 6.
The numbers are positive because both edges happen to be leaving from their respective nodes.
edge_id 7 on the other hand, starts on the right, and ends on the bottom. It's _right_edge is -3, not 3, because edge 3 is arriving at the node.
+28Consider the following simple grid. The _edge_id 3 is highlighted with the starting node at the center.
If you travel in the direction of the line, when you get to the to_node, there are two other edges, 1, and 7. The right edge is the segment you would be on if you turned right.
If on the other hand, you travel in the reverse direction along edge 3, from the outside to the center, at the from_node there are 3 options: 2, 5, 6, Turning right would have you on edge 6.
So the right_edge is 1 and the left edge is 6.
The numbers are positive because both edges happen to be leaving from their respective nodes.
edge_id 7 on the other hand, starts on the right, and ends on the bottom. It's _right_edge is -3, not 3, because edge 3 is arriving at the node.
+28Consider the following simple grid. The _edge_id 3 is highlighted with the starting node at the center.
If you travel in the direction of the line, when you get to the to_node, there are two other edges, 1, and 7. The right edge is the segment you would be on if you turned right.
If on the other hand, you travel in the reverse direction along edge 3, from the outside to the center, at the from_node there are 3 options: 2, 5, 6, Turning right would have you on edge 6.
So the right_edge is 1 and the left edge is 6.
The numbers are positive because both edges happen to be leaving from their respective nodes.
edge_id 7 on the other hand, starts on the right, and ends on the bottom. It's _right_edge is -3, not 3, because edge 3 is arriving at the node.
I assume it has some benefit in graph theory / network traversal, but I admit I've never actually used them for anything.
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