# GLKViewController A view controller that manages an OpenGL ES rendering loop. ``` class GLKViewController ``` ## Overview A [`GLKViewController`](/documentation/GLKit/GLKViewController) object works in conjunction with a [`GLKView`](/documentation/GLKit/GLKView) object to display frames of animation in the view, and also provides standard view controller functionality. To use this class, allocate and initialize a new [`GLKViewController`](/documentation/GLKit/GLKViewController) subclass and set its property to point to a [`GLKView`](/documentation/GLKit/GLKView) object. Then, configure the view controller’s [`preferredFramesPerSecond`](/documentation/GLKit/GLKViewController/preferredFramesPerSecond) property to the desired frame rate your application requires. You can set a delegate or configure other properties on the view controller, such as whether the animation loop is automatically paused or resumed when the application moves into the background. > Note: > When you set the property to point to a ``doc://com.apple.glkit/documentation/GLKit/GLKView`` object, if the view does not already have a delegate, then the view controller is automatically set as the view’s delegate. When active, rendering loop automatically updates the view’s contents each time a new frame must be displayed. Each frame is rendered by the view controller using these steps: 1. The view controller calls its delegate’s [`glkViewControllerUpdate(_:)`](/documentation/GLKit/GLKViewControllerDelegate/glkViewControllerUpdate(_:)) method. Your delegate should update frame data that does not involve rendering the results to the screen. 2. The view controller calls its view’s [`display()`](/documentation/GLKit/GLKView/display()) method. Your view should redraw the frame. ### Subclassing Notes Your application should subclass [`GLKViewController`](/documentation/GLKit/GLKViewController) and override the and methods. Your `viewDidLoad` method should set up your context and any drawable properties and can perform other resource allocation and initialization. Similarly, your class’s `viewDidUnload` method should delete the drawable object and free any unneeded resources. As an alternative to implementing a [`glkViewControllerUpdate(_:)`](/documentation/GLKit/GLKViewControllerDelegate/glkViewControllerUpdate(_:)) method in a delegate, your subclass can provide an update method instead. The method must have the following signature: ```objc - (void)update; ``` ## Topics ### Configuring the Frame rate [`preferredFramesPerSecond`](/documentation/GLKit/GLKViewController/preferredFramesPerSecond) The rate you want the view controller to call the view to update the contents of the view. [`framesPerSecond`](/documentation/GLKit/GLKViewController/framesPerSecond) The actual rate that the view controller attempts to call the view to update its contents. ### Configuring the Delegate [`delegate`](/documentation/GLKit/GLKViewController/delegate) The view controller’s delegate. ### Controlling Frame Updates [`paused`](/documentation/GLKit/GLKViewController/isPaused) A Boolean value that indicates whether the rendering loop is paused. [`pauseOnWillResignActive`](/documentation/GLKit/GLKViewController/pauseOnWillResignActive) A Boolean value that indicates whether the view controller automatically pauses the rendering loop when the application resigns the active state. [`resumeOnDidBecomeActive`](/documentation/GLKit/GLKViewController/resumeOnDidBecomeActive) A Boolean value that indicates whether the view controller automatically resumes the rendering loop when the application becomes active. ### Obtaining Information About View Updates [`framesDisplayed`](/documentation/GLKit/GLKViewController/framesDisplayed) The number of frame updates that have been sent by the view controller since it was created. [`timeSinceFirstResume`](/documentation/GLKit/GLKViewController/timeSinceFirstResume) The amount of time that has passed since first time the view controller resumed sending update events. [`timeSinceLastResume`](/documentation/GLKit/GLKViewController/timeSinceLastResume) The amount of time that has passed since the last time the view controller resumed sending update events. [`timeSinceLastUpdate`](/documentation/GLKit/GLKViewController/timeSinceLastUpdate) The amount of time that has passed since the last time the view controller called the delegate’s [`glkViewControllerUpdate(_:)`](/documentation/GLKit/GLKViewControllerDelegate/glkViewControllerUpdate(_:)) method. [`timeSinceLastDraw`](/documentation/GLKit/GLKViewController/timeSinceLastDraw) The amount of time that has passed since the last time the view controller called the view’s [`display()`](/documentation/GLKit/GLKView/display()) method. ## Relationships ### Conforms To [`UIContentContainer`](/documentation/UIKit/UIContentContainer) [`UIUserActivityRestoring`](/documentation/UIKit/UIUserActivityRestoring) [`UIStateRestoring`](/documentation/UIKit/UIStateRestoring) [`UIAppearanceContainer`](/documentation/UIKit/UIAppearanceContainer) [`UIFocusEnvironment`](/documentation/UIKit/UIFocusEnvironment) [`NSCoding`](/documentation/Foundation/NSCoding) [`UIPasteConfigurationSupporting`](/documentation/UIKit/UIPasteConfigurationSupporting) [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) [`CVarArg`](/documentation/Swift/CVarArg) [`UIActivityItemsConfigurationProviding`](/documentation/UIKit/UIActivityItemsConfigurationProviding) [`Hashable`](/documentation/Swift/Hashable) [`NSExtensionRequestHandling`](/documentation/Foundation/NSExtensionRequestHandling) [`GLKViewDelegate`](/documentation/GLKit/GLKViewDelegate) [`UITraitChangeObservable-67e94`](/documentation/UIKit/UITraitChangeObservable-67e94) [`Sendable`](/documentation/Swift/Sendable) [`UITraitEnvironment`](/documentation/UIKit/UITraitEnvironment) [`SendableMetatype`](/documentation/Swift/SendableMetatype) [`UIResponderStandardEditActions`](/documentation/UIKit/UIResponderStandardEditActions) [`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol) [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) [`Equatable`](/documentation/Swift/Equatable) ### Inherits From [`UIViewController`](/documentation/UIKit/UIViewController) --- Copyright © 2026 Apple Inc. 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