Composition flags control per-pixel transparency and color interpretation. Here's how to avoid halos, dark edges, and inconsistent blending between runtimes.
Direct answer
OpenXR uses compositing flags to inform whether the texture's alpha channel should participate in blending and whether colors arrive unpremultiplied. Without XR_COMPOSITION_LAYER_BLEND_TEXTURE_SOURCE_ALPHA_BIT, the runtime treats the layer's alpha as one. When the application activates transparency, it must correctly declare whether RGB has already been multiplied by alpha; The wrong combination produces halos, darkening, or colored borders on panels and content over passthrough.
Alpha needs to be enabled
Having an RGBA format is not enough; without the source alpha flag, the layer is treated as opaque in composition.
Premultiplication changes math
Assets, render targets and shaders must agree on whether RGB already incorporates alpha. Duplicate or missing conversions appear mainly at the edges.
Layer order changes the result
The runtime composes on the sent sequence. Transparency upon transparency needs a deliberate order consistent with the expected visual effect.
Old bit should not guide architecture
Chromatic aberration correction is deprecated and ignored in known conforming runtimes; new implementations should not depend on it.
Nexus Reading
Define an alpha convention per pipeline, automate edge tests, and validate panels on light, dark, and passthrough backgrounds at every runtime.
FAQ
Does an RGBA texture automatically become transparent?
No. The layer needs to enable the use of source alpha in composition.
What does unpremultiplied alpha mean?
It means that the RGB channels have not yet been multiplied by the alpha value.
How to avoid halos?
Keep asset, shader, render target and composition flag in the same convention and test edges on different backgrounds.
Essential guides to delve deeper into the decision
This editorial analysis was produced by Nexus from the official sources below, consulted on October 27, 2026. The text is original and interprets practical implications for companies.
- Khronos — XrCompositionLayerFlagBits: texture alpha flags, non-premultiplied colors and deprecated bit.
- Khronos — OpenXR 1.1 specification: blending rules, layer order and composition by runtime.
Date reported by main source: OpenXR 1.1.65 consulted on October 27, 2026; technical analysis.