{"action":"closed","issue":{"url":"https://api.github.com/repos/KhronosGroup/glTF/issues/1409","repository_url":"https://api.github.com/repos/KhronosGroup/glTF","labels_url":"https://api.github.com/repos/KhronosGroup/glTF/issues/1409/labels{/name}","comments_url":"https://api.github.com/repos/KhronosGroup/glTF/issues/1409/comments","events_url":"https://api.github.com/repos/KhronosGroup/glTF/issues/1409/events","html_url":"https://github.com/KhronosGroup/glTF/issues/1409","id":345539398,"node_id":"MDU6SXNzdWUzNDU1MzkzOTg=","number":1409,"title":"STEP interpolation, first interval","user":{"login":"andreasplesch","id":6171115,"node_id":"MDQ6VXNlcjYxNzExMTU=","avatar_url":"https://avatars0.githubusercontent.com/u/6171115?v=4","gravatar_id":"","url":"https://api.github.com/users/andreasplesch","html_url":"https://github.com/andreasplesch","followers_url":"https://api.github.com/users/andreasplesch/followers","following_url":"https://api.github.com/users/andreasplesch/following{/other_user}","gists_url":"https://api.github.com/users/andreasplesch/gists{/gist_id}","starred_url":"https://api.github.com/users/andreasplesch/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/andreasplesch/subscriptions","organizations_url":"https://api.github.com/users/andreasplesch/orgs","repos_url":"https://api.github.com/users/andreasplesch/repos","events_url":"https://api.github.com/users/andreasplesch/events{/privacy}","received_events_url":"https://api.github.com/users/andreasplesch/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":3,"created_at":"2018-07-29T15:28:11Z","updated_at":"2018-07-30T14:38:52Z","closed_at":"2018-07-30T14:38:52Z","author_association":"NONE","body":"https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animation-samplerinterpolation\r\nsays:\r\n```\r\n\"STEP\" The animated values remain constant to the output of the first keyframe, until the next keyframe. The number of output elements must equal the number of input elements.\r\n```\r\nkey frames as keys and output:\r\n```\r\nstart - - | - - | - - | -\r\nout   x x 6 x x 8 x x 9 x\r\n```\r\nStart is t=0. The vertical bars are key frames. The first key frame has an output value of 6. x are the values which I want to get right.\r\n\r\nClamping before the first key frame means\r\n```\r\nstart - - | - - | - - | -\r\nout   6 6 6 x x 8 x x 9 x\r\n```\r\nThis is also consistent with what the STEP interpolation language says.\r\n\r\nThe 'next key frame' is the second one, so 'until' should mean continuing like this:\r\n\r\n```\r\nstart - - | - - | - - | -\r\nout   6 6 6 6 6 8 x x 9 x\r\n```\r\n\r\nIs continuing without a change after the first key frame the intended meaning ? It probably is.\r\n\r\nThe alternative is to use 8 for the interval between key frames one and two.\r\n\r\nThen the value steps:\r\n\r\n```\r\nstart - - | - - | - - | -\r\nout   6 6 6 6 6 8 8 8 9 x\r\n```\r\n\r\nand then again, also clamping after the last key frame\r\n\r\n```\r\nstart - - | - - | - - | -\r\nout   6 6 6 6 6 8 8 8 9 9\r\n```\r\n\r\nDoes that look correct ?"}}
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