{"action":"created","issue":{"url":"https://api.github.com/repos/landgreen/landgreen.github.io/issues/5","repository_url":"https://api.github.com/repos/landgreen/landgreen.github.io","labels_url":"https://api.github.com/repos/landgreen/landgreen.github.io/issues/5/labels{/name}","comments_url":"https://api.github.com/repos/landgreen/landgreen.github.io/issues/5/comments","events_url":"https://api.github.com/repos/landgreen/landgreen.github.io/issues/5/events","html_url":"https://github.com/landgreen/landgreen.github.io/pull/5","id":328351474,"node_id":"MDExOlB1bGxSZXF1ZXN0MTkxOTE0Mjk1","number":5,"title":"Fix applyGravity() to avoid precessing circular orbits","user":{"login":"paulmasson","id":3289562,"node_id":"MDQ6VXNlcjMyODk1NjI=","avatar_url":"https://avatars2.githubusercontent.com/u/3289562?v=4","gravatar_id":"","url":"https://api.github.com/users/paulmasson","html_url":"https://github.com/paulmasson","followers_url":"https://api.github.com/users/paulmasson/followers","following_url":"https://api.github.com/users/paulmasson/following{/other_user}","gists_url":"https://api.github.com/users/paulmasson/gists{/gist_id}","starred_url":"https://api.github.com/users/paulmasson/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/paulmasson/subscriptions","organizations_url":"https://api.github.com/users/paulmasson/orgs","repos_url":"https://api.github.com/users/paulmasson/repos","events_url":"https://api.github.com/users/paulmasson/events{/privacy}","received_events_url":"https://api.github.com/users/paulmasson/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":6,"created_at":"2018-06-01T01:41:26Z","updated_at":"2018-06-14T21:19:51Z","closed_at":"2018-06-02T19:23:39Z","author_association":"CONTRIBUTOR","pull_request":{"url":"https://api.github.com/repos/landgreen/landgreen.github.io/pulls/5","html_url":"https://github.com/landgreen/landgreen.github.io/pull/5","diff_url":"https://github.com/landgreen/landgreen.github.io/pull/5.diff","patch_url":"https://github.com/landgreen/landgreen.github.io/pull/5.patch"},"body":"This small edit will avoid the precessing circular orbits mentioned on Reddit:\r\n\r\nhttps://www.reddit.com/r/Physics/comments/8my98x/online_physics_course_notes_with_javascript/dzrfnki/\r\n\r\nI'm assuming you added the offset to prevent infinities in gravitational collisions, but the value is much too large. If you want to keep it in, you could try something much smaller, but it would probably be better to handle collisions in other ways.\r\n\r\nFYI your technique of integration goes by the name of the [Euler method](https://en.wikipedia.org/wiki/Euler_method). It's fine for small time steps and total integration times that are not too large."},"comment":{"url":"https://api.github.com/repos/landgreen/landgreen.github.io/issues/comments/397441847","html_url":"https://github.com/landgreen/landgreen.github.io/pull/5#issuecomment-397441847","issue_url":"https://api.github.com/repos/landgreen/landgreen.github.io/issues/5","id":397441847,"node_id":"MDEyOklzc3VlQ29tbWVudDM5NzQ0MTg0Nw==","user":{"login":"paulmasson","id":3289562,"node_id":"MDQ6VXNlcjMyODk1NjI=","avatar_url":"https://avatars2.githubusercontent.com/u/3289562?v=4","gravatar_id":"","url":"https://api.github.com/users/paulmasson","html_url":"https://github.com/paulmasson","followers_url":"https://api.github.com/users/paulmasson/followers","following_url":"https://api.github.com/users/paulmasson/following{/other_user}","gists_url":"https://api.github.com/users/paulmasson/gists{/gist_id}","starred_url":"https://api.github.com/users/paulmasson/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/paulmasson/subscriptions","organizations_url":"https://api.github.com/users/paulmasson/orgs","repos_url":"https://api.github.com/users/paulmasson/repos","events_url":"https://api.github.com/users/paulmasson/events{/privacy}","received_events_url":"https://api.github.com/users/paulmasson/received_events","type":"User","site_admin":false},"created_at":"2018-06-14T21:19:51Z","updated_at":"2018-06-14T21:19:51Z","author_association":"CONTRIBUTOR","body":"Like any developer, I'm always interested in having people use my library. I've tried reaching out a bit with no substantive responses, and a project can't really grow without input from others. You're exactly the sort of forward-looking educator whose feedback would be most appreciated.\r\n\r\nThat being said, it depends on what you want to visualize and how. You already know about the two main options available now: D3 and JSXGraph. I personally found the learning curve for D3 so steep that is was simpler to write my own SVG plotting code, but it produces a certain look that people like. I don't like the interface for JSXGraph, since I wanted to replicate the feel of Mathematica's Manipulate command, but it does handle touch events like D3. Neither library does 3D, however.\r\n\r\nYour website already has lots of animations, and that's one area where my project needs work. Since it takes little processing effort to produce reasonable SVGs, I can fudge 2D animations by simply replacing the output in an animation frame loop, but that's not the best way to do it. That approach won't work at all for 3D as I'm presenting it now. I've been thinking about ways to improve that but again input from users would be most helpful.\r\n\r\nI'd certainly encourage you to try out MathCell and let me know if you find it easy to use or not. Since I wrote it I think it's simpler to get results for my use cases than D3 or JSXGraph would be, but I'm always eager to know what others think. As a JavaScript coder, you'll notice that my functions are in the global namespace: that's to make them work like Mathematica and SageMath commands, but could potentially lead to conflicts.\r\n\r\nIf you find there are visualizations you'd like to do with MathCell that can't be done yet, then please open an issue and describe the situation. I'm always adding new features that I need to use and can do the same for others, but again I need input. Perhaps that would be an interesting way to spend part of your summer!"}}
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