# init(circleOfRadius:) Creates a circular physics body centered on the owning node’s origin. ``` init(circleOfRadius r: CGFloat) ``` ## Parameters `r` The radius of the circle. ## Return Value A new volume-based physics body. ## Discussion The following code shows the code that creates the physics body for a spherical or circular object. Because the physics body is attached to a sprite object, it usually needs volume. In this case, the sprite image is assumed to closely approximate a circle centered on the anchor point, so the radius of the circle is calculated and used to create the physics body. Listing 1. A physics body for a circular sprite ```swift let sprite = SKSpriteNode(imageNamed: "sphere.png") sprite.physicsBody = SKPhysicsBody(circleOfRadius: sprite.size.width / 2) sprite.physicsBody?.isDynamic = true ``` If the physics body were significantly smaller than the sprite’s image, the data used to create the physics body might need to be provided by some other source, such as a property list. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)