{"action":"created","issue":{"url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/issues/66","repository_url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles","labels_url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/issues/66/labels{/name}","comments_url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/issues/66/comments","events_url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/issues/66/events","html_url":"https://github.com/AnalyticalGraphicsInc/3d-tiles/issues/66","id":129713478,"number":66,"title":"Suggestion for hierarchies in batch table","user":{"login":"arneschilling","id":7847218,"avatar_url":"https://avatars.githubusercontent.com/u/7847218?v=3","gravatar_id":"","url":"https://api.github.com/users/arneschilling","html_url":"https://github.com/arneschilling","followers_url":"https://api.github.com/users/arneschilling/followers","following_url":"https://api.github.com/users/arneschilling/following{/other_user}","gists_url":"https://api.github.com/users/arneschilling/gists{/gist_id}","starred_url":"https://api.github.com/users/arneschilling/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/arneschilling/subscriptions","organizations_url":"https://api.github.com/users/arneschilling/orgs","repos_url":"https://api.github.com/users/arneschilling/repos","events_url":"https://api.github.com/users/arneschilling/events{/privacy}","received_events_url":"https://api.github.com/users/arneschilling/received_events","type":"User","site_admin":false},"labels":[{"id":357480509,"url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/labels/draft%201.0","name":"draft 1.0","color":"0e8a16","default":false}],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":11,"created_at":"2016-01-29T09:30:30Z","updated_at":"2016-11-02T10:19:55Z","closed_at":null,"body":"We are working on ideas for supporting hierarchies in B3DM. \nThe background is that we are working with 3D GIS and BIM data (as CityGML or IFC), which are usually more complicated than 3D viz datasets. We want to preserve as much information as possible.\nCurrently there is a way to group nodes in GLTF.  However, we also want to optimzie rendering as much as possible and make use of batches including attribute tables in B3DM.\nIn our scenarios, we have complex input data with groups, hierarchies and attributes on different levels. For instance,\na building has a unique id and a set of attributes and properties. The parts the building is made of also has a set of attributes, which are usually different. Sometimes we have 3 hierarchy levels and more.\nthe application we are working on must support selecting and highlighting entities at all available levels and display the attached attributes (as key value pairs).\nWe want to click on buildings and display building specific attributes and we also want to click on building parts and display component specific (wall, roof, window, door...) attributes without switching \nto another data set with different configuration. The behavior of what kind of element is selected is controlled by a toggle button or by other means.\n\nThe current design of the batch table is quite simple, it is basically a 2D grid. \nNow the question is how we group together batches and attach attributes to these groups.\n\nWe found out that the number of columns is flexible and that its not restricted to the number of batches. We can extend the batch table to include additional columns representing abstract features for which we can include attitional attributes.\nThis is nowhere specified, but it currently happily consumed by Cesium. \n\n@jbo023 has set up a demo application\n[http://hosting.virtualcitysystems.de/demos/hierarchy/](http://hosting.virtualcitysystems.de/demos/hierarchy/)\nUse the CityGML Explorer to access attributes and toggle between building selection and part selection using the buttons on the right.\n\nExample B3DM file:\n[http://hosting.virtualcitysystems.de/demos/hierarchy/examples/data/buildings_semantic/15/35210/6826.b3dm](http://hosting.virtualcitysystems.de/demos/hierarchy/examples/data/buildings_semantic/15/35210/6826.b3dm)\n\nThere is no formal specification of our approach because we see it as workaround taking into account the current limitations of B3DM.\nPlease let us know in case somebody is working on a similar topic. We are happy to discuss possible solutions.\n\nAs to the example file above, you will see batch table with ids, attributes (ignore the strange format for now..) and a row called parentPosition.\nThe latter is providing the information on how things are grouped together. E.g the first two entries in this row are 1243, which means that these batches are grouped together.\nThe id of this group can be found in the id array at position 1243. However, there is no batch with this number, its just an abtract group feature.\n\nWhat do you think of this approach? \nHas anybody alternative ideas or suggestions to accomplish this? Our intention is to include this feature in the 3D Tiles specification so that we can base our framework on the master branch. We can try to formally describe our concept in the git repo and create a pull request.\n\nbest regards,\nArne\n"},"comment":{"url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/issues/comments/257825214","html_url":"https://github.com/AnalyticalGraphicsInc/3d-tiles/issues/66#issuecomment-257825214","issue_url":"https://api.github.com/repos/AnalyticalGraphicsInc/3d-tiles/issues/66","id":257825214,"user":{"login":"jbo023","id":4146115,"avatar_url":"https://avatars.githubusercontent.com/u/4146115?v=3","gravatar_id":"","url":"https://api.github.com/users/jbo023","html_url":"https://github.com/jbo023","followers_url":"https://api.github.com/users/jbo023/followers","following_url":"https://api.github.com/users/jbo023/following{/other_user}","gists_url":"https://api.github.com/users/jbo023/gists{/gist_id}","starred_url":"https://api.github.com/users/jbo023/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jbo023/subscriptions","organizations_url":"https://api.github.com/users/jbo023/orgs","repos_url":"https://api.github.com/users/jbo023/repos","events_url":"https://api.github.com/users/jbo023/events{/privacy}","received_events_url":"https://api.github.com/users/jbo023/received_events","type":"User","site_admin":false},"created_at":"2016-11-02T10:19:55Z","updated_at":"2016-11-02T10:19:55Z","body":"At a first glance this looks like a nice concept. \r\nIn the paragraph CLASS_ID you probably meant \"item 3 is wall1\", if not I didn't get the concept yet. \r\nAlso the PARENT_COUNT row probably has one item to much.\r\n\r\n"}}
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