{"action":"created","issue":{"url":"https://api.github.com/repos/viblo/pymunk/issues/119","repository_url":"https://api.github.com/repos/viblo/pymunk","labels_url":"https://api.github.com/repos/viblo/pymunk/issues/119/labels{/name}","comments_url":"https://api.github.com/repos/viblo/pymunk/issues/119/comments","events_url":"https://api.github.com/repos/viblo/pymunk/issues/119/events","html_url":"https://github.com/viblo/pymunk/issues/119","id":244774543,"number":119,"title":"Collision handling sensitive to order in which objects are added","user":{"login":"Rick-C-137","id":5832271,"avatar_url":"https://avatars0.githubusercontent.com/u/5832271?v=4","gravatar_id":"","url":"https://api.github.com/users/Rick-C-137","html_url":"https://github.com/Rick-C-137","followers_url":"https://api.github.com/users/Rick-C-137/followers","following_url":"https://api.github.com/users/Rick-C-137/following{/other_user}","gists_url":"https://api.github.com/users/Rick-C-137/gists{/gist_id}","starred_url":"https://api.github.com/users/Rick-C-137/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/Rick-C-137/subscriptions","organizations_url":"https://api.github.com/users/Rick-C-137/orgs","repos_url":"https://api.github.com/users/Rick-C-137/repos","events_url":"https://api.github.com/users/Rick-C-137/events{/privacy}","received_events_url":"https://api.github.com/users/Rick-C-137/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2017-07-21T20:25:13Z","updated_at":"2017-07-24T20:23:22Z","closed_at":null,"body":"I'm building simple block towers with rectangular blocks. The top y-coordinate of one block is exactly equal to the bottom y-coordinate of the one above it (e.g. the top of block 1 is y=50 and the bottom of block 2 resting on top of it is also y=50). I discovered that if blocks are added to the space in a different order, say block 1 then 2 then 3 then 4, ..., versus 2, 1, 5, 3, ..., the collisions resolutions are handled differently at the outset, causing divergent simulations. Is there some reason for this that you can think of? Is it generally not good practice to make the shapes exactly touch, like I have?"},"comment":{"url":"https://api.github.com/repos/viblo/pymunk/issues/comments/317543146","html_url":"https://github.com/viblo/pymunk/issues/119#issuecomment-317543146","issue_url":"https://api.github.com/repos/viblo/pymunk/issues/119","id":317543146,"user":{"login":"viblo","id":1195272,"avatar_url":"https://avatars3.githubusercontent.com/u/1195272?v=4","gravatar_id":"","url":"https://api.github.com/users/viblo","html_url":"https://github.com/viblo","followers_url":"https://api.github.com/users/viblo/followers","following_url":"https://api.github.com/users/viblo/following{/other_user}","gists_url":"https://api.github.com/users/viblo/gists{/gist_id}","starred_url":"https://api.github.com/users/viblo/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/viblo/subscriptions","organizations_url":"https://api.github.com/users/viblo/orgs","repos_url":"https://api.github.com/users/viblo/repos","events_url":"https://api.github.com/users/viblo/events{/privacy}","received_events_url":"https://api.github.com/users/viblo/received_events","type":"User","site_admin":false},"created_at":"2017-07-24T20:23:21Z","updated_at":"2017-07-24T20:23:21Z","body":"Im on vacation without computer now so I can't give a full reply. But in\ngeneral Im not surprised, different order of objects could generate\ndifferent collision response.\n\nIt also feels reasonable to add objects already touching exactly on top of\neach other. Note that the way pymunk works objects always sink into each\nother a little bit, so even if you add them exactly on top each other they\nmight sink into each other when simulation is started.\n\nOn Jul 21, 2017 22:25, \"Chris Bates\" <notifications@github.com> wrote:\n\nI'm building simple block towers with rectangular blocks. The top\ny-coordinate of one block is exactly equal to the bottom y-coordinate of\nthe one above it (e.g. the top of block 1 is y=50 and the bottom of block 2\nresting on top of it is also y=50). I discovered that if blocks are added\nto the space in a different order, say block 1 then 2 then 3 then 4, ...,\nversus 2, 1, 5, 3, ..., the collisions resolutions are handled differently\nat the outset, causing divergent simulations. Is there some reason for this\nthat you can think of? Is it generally not good practice to make the shapes\nexactly touch, like I have?\n\n—\nYou are receiving this because you are subscribed to this thread.\nReply to this email directly, view it on GitHub\n<https://github.com/viblo/pymunk/issues/119>, or mute the thread\n<https://github.com/notifications/unsubscribe-auth/ABI9CBULpk-6dkSCQSMH4ArqckKKFw7wks5sQQkpgaJpZM4Of2sL>\n.\n"}}
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