Safari 27: Globe atmosphere vertex shader fails to link through ANGLE/Metal

[kinglau66]

What happened?

CesiumJS fails to render in Safari 27 because the globe atmosphere vertex shader cannot be linked by Safari’s ANGLE/Metal backend.

Error

Safari reports an internal Metal compilation error involving ANGLE_Out, thread float3, and __metal_generic float3. Full logs are attached.
Console.txt

Workaround

Using local variables for the atmosphere-scattering outputs before assigning the vertex outputs links successfully. Disabling both fog and ground atmosphere also avoids the failure:

viewer.scene.globe.showGroundAtmosphere = false;
viewer.scene.fog.enabled = false;

Could GlobeVS.glsl use local temporary variables for the computeAtmosphereScattering outputs to avoid this Safari translator issue?

Console.txt

Reproduction steps

The issue is reproducible in Cesium Sandcastle when fog or ground atmosphere is enabled. Chrome renders the same scene correctly.

Sandcastle example

https://sandcastle.cesium.com

Environment

• CesiumJS: 1.137; the same shader pattern remains in current versions
• Safari: 27.0 (22625.1.24.11.2)
• macOS: 27.0 (26A5388g)
• GPU: Apple M4 Pro

AI acknowledgment

• I used AI to generate this issue report.
• (If the above is checked) I have reviewed the AI-generated content before submitting.