Get Neighbour-Nodes from a node about octomap HOT 10 CLOSED

It's not implemented right now, the nodes have no information about their direct neighbors. What you can do is get the node's key (from iterator), then search for that key +/-1 in each dimension.

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Hi Armin,
thanks for answering! If I understood your correctly, you mean the following steps:

1. find a node by key
2. get its coordinates (x,y,z)
3. calculate neighbouring 8 coordinates
4. search the nodes for every of the generated coordinates.

However, I would prefer to use references to parent nodes. I extended the createChild(int) method in the OcTreeNode class and if you like, you can accept the merge request from my fork.

By the way! This is a superior framework! Works on windows and linux. (even gs 4.7 :) )
Thank you very much!

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The straighforward way would be:

1. find a node by key (from coordinates or iterator)
2. add / subtract 1 from the key values to driectly get the neighbor key
3. search neighbor node by key

See my comments in your pull request for the parent pointers.

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An alternative way would be to temporarily store parent information in a recursive call while the tree is traversed, and use that for faster neighbor queries. Some experimental work in that direction was started in the OcTreeLUT classes (unfinished / unused right now).

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Oh thank you!
the 3 steps sound promising. Is there a short explanation of how the key is generated? In which direction do I traverse the nodes if I add 1 or subtract 1?

Edit: Sorry for the last message. I found this paper, which is referenced by the OcTreeLUT : http://www.cs.umd.edu/~hjs/pubs/SameCG89.pdf
Great stuff! :)

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Have a look at coordToKey, the keys are a simple discretization of the coordinates. So +1 on the first dimension will be +res in x.

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Does this also apply to keys of nodes in coarser resolution? Is +1 still +res (getResolution()) or +res in this depth of the tree?

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Keys only represent the coordinates at the tree resolution (voxel coordinates). With a depth and the function computeIndexKey(..) you can get a coarser key, but need to consider the depth yourself (e.g. add +2 at depth 15, +4 at 14 and so on).

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I am facing similar issue. I am feeding Octomap::PointCloud. by using iterator I found the octreeNode of each occupied node. But How to find keys of each occupied node from OctreeNode ?
I want to find the neighbours of each occupied node.

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Once upon a time there was OcTreeLUT that implemented a lookup table to compute keys of neighbor cells directly.

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