A specialized view that creates, configures, and displays Metal objects.
- iOS 9.0+
- macOS 10.11+
- Mac Catalyst 13.0+
- tvOS 9.0+
MTKView class provides a default implementation of a Metal-aware view that you can use to render graphics using Metal and display them onscreen. When asked, the view provides a
MTLRender object that points at a texture for you to render new contents into. Optionally, an
MTKView can create depth and stencil textures for you and any intermediate textures needed for antialiasing. The view uses a
CAMetal to manage the Metal drawable objects.
Configuring the Drawing Behavior
The MTKView class supports three drawing modes:
Timed updates: The view redraws its contents based on an internal timer. In this case, which is the default behavior, both
enableare set to
Set Needs Display
NO. Use this mode for games and other animated content that’s regularly updated.
Draw notifications: The view redraws itself when something invalidates its contents, usually because of a call to
setor some other view-related behavior. In this case, set
Set Needs Display
YES. Use this mode for apps with a more traditional workflow, where updates happen when data changes, but not on a regular timed interval.
Explicit drawing: The view redraws its contents only when you explicitly call the
drawmethod. In this case, set
Set Needs Display
NO. Use this mode to create your own custom workflow.
Drawing the View's Contents
Regardless of drawing mode, when the view needs to update its contents, it calls the
draw method when that method has been overridden by a subclass, or
draw on the view’s delegate if the subclass doesn’t override it. You should either subclass
MTKView or provide a delegate, but not both.
In your drawing method, you obtain a render pass descriptor from the view, render into it, and then present the associated drawable.
Obtaining a Drawable from a MetalKit View
MTKView is backed by a
CAMetal. In your renderer, implement the
MTKView protocol to interact with a MetalKit view. Call the MetalKit view’s
current property to obtain a render pass descriptor configured for the current frame:
When you read this property, Core Animation implicitly obtains a drawable for the current frame and stores it in the
current property. It then configures a render pass descriptor to draw into that drawable, including any depth, stencil, and antialiasing textures as necessary. The view configures this render pass using the default store and load actions. You can adjust the descriptor further before using it to create a
Obtain drawables as late as possible; preferably, immediately before encoding your onscreen render pass.
Registering the Drawable's Presentation
After rendering the contents, you must present the drawable to update the view’s contents. The most convenient way to present the content is to call the
present method on the command buffer. Then, call the
commit method to submit the command buffer to a GPU:
When a command queue schedules a command buffer for execution, the drawable tracks all render or write requests on itself in that command buffer. The operating system doesn't present the drawable onscreen until the commands have finished executing. By asking the command buffer to present the drawable, you guarantee that presentation happens after the command queue has scheduled this command buffer. Don’t wait for the command buffer to finish executing before registering the drawable’s presentation.