--- title: Predictive Joint Limits :: Box2D | daily.dev description: Discrete time-stepping in physics engines can let fast-moving joints temporarily violate their limits, causing visual glitches like a filing cabinet drawer... canonical: https://daily.dev/posts/predictive-joint-limits-box2d-kkphe7e4o twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Predictive Joint Limits :: Box2D | daily.dev og:description: Discrete time-stepping in physics engines can let fast-moving joints temporarily violate their limits, causing visual glitches like a filing cabinet drawer... og:url: https://daily.dev/posts/predictive-joint-limits-box2d-kkphe7e4o og:image: https://api.daily.dev/og/posts/KKPHe7e4o.png og:image:alt: Predictive Joint Limits :: 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. # Predictive Joint Limits :: Box2D **[ Box2D ](https://daily.dev/sources/box2d)** · 4 min read · 0 upvotes · 0 comments ## Summary Discrete time-stepping in physics engines can let fast-moving joints temporarily violate their limits, causing visual glitches like a filing cabinet drawer overshooting its track. Box2D's creator explains a predictive joint limit technique, inspired by Vincent Robert's continuous physics approach, that measures the gap between current position and limit, then anticipates whether velocity will close that gap and applies an impulse so the limit is reached but never exceeded. The fix is cheap to implement, removes the need to track limit state in the velocity solver, but requires separate lower and upper limit constraints since the velocity constraint value can flip sign mid-solve. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How can I prevent a prismatic joint limit from being violated when objects move fast in a physics simulation? Use a predictive joint limit approach: measure the gap between the current position and the limit, then use current velocity to estimate whether the gap will close before the next time step. If it would, apply an impulse in the velocity solver so the limit is reached but not exceeded, instead of only reacting after the limit is violated. This requires separate lower and upper limit constraints since the velocity constraint value can flip sign during solver iterations. _daily.dev surfaces engine-level physics techniques like this for developers refining collision and constraint solvers._ ### Why does a fast-moving drawer using a prismatic joint temporarily clip through its limit in Box2D? Discrete time-stepping only checks joint limits after they have already been violated, so with fast movement or a large time step, a body like a drawer can briefly end up in a position beyond its intended lower or upper limit before the solver corrects it. This reactive behavior causes a visible glitch even though the constraint is eventually enforced. _developers debugging physics glitches can find deep dives like this via daily.dev's coverage of game engine internals._ ## Similar posts on daily.dev - [A Physics Engine with Incremental Rollback • Easel](https://daily.dev/posts/a-physics-engine-with-incremental-rollback-easel-smqrkuh1s) · Hacker News · 1 upvotes · 0 comments --- [View this post on daily.dev](https://daily.dev/posts/predictive-joint-limits-box2d-kkphe7e4o) ```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":"Predictive Joint Limits :: Box2D","url":"https://daily.dev/posts/predictive-joint-limits-box2d-kkphe7e4o","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/predictive-joint-limits-box2d-kkphe7e4o"},"datePublished":"2026-08-23T12:16:49.884Z","dateModified":"2026-08-23T12:59:20.271Z","description":"Discrete time-stepping in physics engines can let fast-moving joints temporarily violate their limits, causing visual glitches like a filing cabinet drawer...","image":"https://media.daily.dev/image/upload/s--VDukGCjf--/f_auto/v1722860399/public/Placeholder%2002","thumbnailUrl":"https://media.daily.dev/image/upload/s--VDukGCjf--/f_auto/v1722860399/public/Placeholder%2002","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/predictive-joint-limits-box2d-kkphe7e4o","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"","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":"Predictive Joint Limits :: Box2D"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/predictive-joint-limits-box2d-kkphe7e4o#faq","mainEntity":[{"@type":"Question","name":"How can I prevent a prismatic joint limit from being violated when objects move fast in a physics simulation?","acceptedAnswer":{"@type":"Answer","text":"Use a predictive joint limit approach: measure the gap between the current position and the limit, then use current velocity to estimate whether the gap will close before the next time step. If it would, apply an impulse in the velocity solver so the limit is reached but not exceeded, instead of only reacting after the limit is violated. This requires separate lower and upper limit constraints since the velocity constraint value can flip sign during solver iterations. daily.dev surfaces engine-level physics techniques like this for developers refining collision and constraint solvers."}},{"@type":"Question","name":"Why does a fast-moving drawer using a prismatic joint temporarily clip through its limit in Box2D?","acceptedAnswer":{"@type":"Answer","text":"Discrete time-stepping only checks joint limits after they have already been violated, so with fast movement or a large time step, a body like a drawer can briefly end up in a position beyond its intended lower or upper limit before the solver corrects it. This reactive behavior causes a visible glitch even though the constraint is eventually enforced. developers debugging physics glitches can find deep dives like this via daily.dev's coverage of game engine internals."}}]} ```