BloomComponent
The BloomComponent adds a luminous glow effect around bright objects in the scene by extracting and blurring the brightest parts of the image, then combining them back with the original rendering. If scope is set to unbounded Bloom will be computed on the entire screen. If scope is set to hierarchical multiple Bloom Components can be used to opt in only the regions around certain objects for blooming.
Declaration
struct BloomComponentOverview
Bloom is available on devices with Apple7 GPU family feature support. Note: On visionOS, Bloom only works in an immersive space and will have no effect in a shared space.
To adjust the appearance of the bloom effect, you also need a BloomOptionsComponent
Example Code:
// Add the bloom component to the root and set it to unbounded.
// This enables bloom in the scene with default parameters
var bloomComponent = BloomComponent()
bloomComponent.scope = .unbounded
self.root.components.set(bloomComponent)
// Add the bloom options component to the root.
// Set strength 1 for a bright effect and threshold 0 so that
// everything blooms no matter how dim.
var bloomOptionsComponent = BloomOptionsComponent()
bloomOptionsComponent.strength = 1
bloomOptionsComponent.threshold = 0
self.root.components.set(bloomOptionsComponent)Performance and thermal state
Bloom is a screen-space effect, so its cost scales with how much of the screen it touches. There are two distinct contributions to keep in mind:
Applying the bloom is proportional to the on-screen size of the bloomers — the bright regions that exceed the threshold. Larger and brighter bloomers and a larger blurRadius increase this cost.
Searching for bloom is a separate step with a large cost that is proportional to the portion of the screen scanned for bright pixels. With unbounded this scans the entire screen regardless of how much of the scene actually blooms.
You can shrink the searched region — and therefore this large cost — by using hierarchical and attaching a BloomComponent to the entities that should bloom. Bloom is then only searched for and applied within the screen-space bounds of those entity hierarchies. Prefer hierarchical whenever you know which objects bloom; reserve unbounded for cases where bright pixels can appear anywhere on screen.
Excessive bloom may contribute to user-noticeable frame drops and can cause the device to heat up in graphically demanding scenes. Monitor the thermal state and shrink the bloom region (prefer hierarchical over unbounded), lower the blurRadius, raise the threshold, or disable bloom entirely if necessary.
To stay responsive to the device’s available thermal headroom, read ProcessInfo.processInfo.thermalState and observe ProcessInfo.thermalStateDidChangeNotification to react when it changes. As the reported state moves from .fair toward .serious and .critical, reduce bloom’s footprint.