--- title: Stuck Inside :: Box2D | daily.dev description: An exploration of convex decomposition for physics collision shapes, using a table-and-beam example to show how independent collision pairs in Box2D can fight... canonical: https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Stuck Inside :: Box2D | daily.dev og:description: An exploration of convex decomposition for physics collision shapes, using a table-and-beam example to show how independent collision pairs in Box2D can fight... og:url: https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj og:image: https://api.daily.dev/og/posts/M2eWpkfzj.png og:image:alt: Stuck Inside :: Box2D og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Stuck Inside :: Box2D **[ Box2D ](https://daily.dev/sources/box2d)** · 4 min read · 0 upvotes · 0 comments ## Summary An exploration of convex decomposition for physics collision shapes, using a table-and-beam example to show how independent collision pairs in Box2D can fight each other and leave objects visually stuck. The author explains why naive convex decomposition creates internal faces that cause this problem, lists the complex engineering steps needed to fix it properly, and instead recommends a simpler practical technique: extending legs/shapes so they overlap, eliminating the channel where objects get trapped. The piece argues manual, human-authored collision geometry often beats fully automated decomposition algorithms. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why do objects get stuck between convex decomposed collision shapes in a physics engine like Box2D? Objects get stuck because the physics engine treats each convex piece as an independent collision pair unaware of the others. For example, a beam jammed between a table top and two legs creates three separate pairs (beam-top, beam-left-leg, beam-right-leg), each generating contact points that push in conflicting directions, so the solver fights itself and the beam never gets ejected. _daily.dev surfaces practical fixes like this for developers debugging physics engine collision edge cases._ ### How can you prevent objects from getting stuck in convex decomposed collision geometry without rewriting the collision algorithm? Extend the convex pieces so they overlap rather than meet flush, removing the channel where another object could wedge itself in. For a table, extending the legs up to the table top eliminates the gap where a beam could get stuck, and combining this with limiting overlap of parallel surfaces avoids redundant contact points while still ejecting overlapping shapes immediately. _Teams tuning collision authoring workflows can track these kinds of game physics tricks on daily.dev._ ## Similar posts on daily.dev - [SIMD for Collision :: Box2D](https://daily.dev/posts/simd-for-collision-box2d-wsosdjqbv) · Lobsters · 0 upvotes · 0 comments - [Inscribed Spheres :: Box2D](https://daily.dev/posts/inscribed-spheres-box2d-dvq55o0po) · Box2D · 0 upvotes · 0 comments - [PhysicsBox. Adding physics to compose driven projects](https://daily.dev/posts/physicsbox-adding-physics-to-compose-driven-projects-zjhjihxz9) · ProAndroidDev · 1 upvotes · 0 comments --- Tags: [#game-development](https://daily.dev/tags/game-development) [View this post on daily.dev](https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Stuck Inside :: Box2D","url":"https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj"},"datePublished":"2026-08-23T12:16:48.890Z","dateModified":"2026-08-23T12:18:18.758Z","description":"An exploration of convex decomposition for physics collision shapes, using a table-and-beam example to show how independent collision pairs in Box2D can fight...","image":"https://media.daily.dev/image/upload/s--P4t4XyoV--/f_auto/v1722860399/public/Placeholder%2001","thumbnailUrl":"https://media.daily.dev/image/upload/s--P4t4XyoV--/f_auto/v1722860399/public/Placeholder%2001","isAccessibleForFree":true,"articleSection":"\n \n Box2D \n \n ","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"\n \n Box2D \n \n ","logo":"https://media.daily.dev/image/upload/s--fmoS1AL5--/f_auto,q_auto/v1787487406/logos/box2d?_a=BAMAMicg0","url":"https://daily.dev/sources/box2d"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"game-development","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"\n \n Box2D \n \n ","item":"https://daily.dev/sources/box2d"},{"@type":"ListItem","position":3,"name":"Stuck Inside :: Box2D"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/stuck-inside-box2d-m2ewpkfzj#faq","mainEntity":[{"@type":"Question","name":"Why do objects get stuck between convex decomposed collision shapes in a physics engine like Box2D?","acceptedAnswer":{"@type":"Answer","text":"Objects get stuck because the physics engine treats each convex piece as an independent collision pair unaware of the others. For example, a beam jammed between a table top and two legs creates three separate pairs (beam-top, beam-left-leg, beam-right-leg), each generating contact points that push in conflicting directions, so the solver fights itself and the beam never gets ejected. daily.dev surfaces practical fixes like this for developers debugging physics engine collision edge cases."}},{"@type":"Question","name":"How can you prevent objects from getting stuck in convex decomposed collision geometry without rewriting the collision algorithm?","acceptedAnswer":{"@type":"Answer","text":"Extend the convex pieces so they overlap rather than meet flush, removing the channel where another object could wedge itself in. For a table, extending the legs up to the table top eliminates the gap where a beam could get stuck, and combining this with limiting overlap of parallel surfaces avoids redundant contact points while still ejecting overlapping shapes immediately. Teams tuning collision authoring workflows can track these kinds of game physics tricks on daily.dev."}}]} ```