From 56ed93a220c3477b31b27545e3b137dd5d7e48bc Mon Sep 17 00:00:00 2001
From: zhaochen <453157936@qq.com>
Date: Fri, 17 Jul 2026 11:30:17 +0800
Subject: [PATCH 1/2] Fix PolylineGlowMaterial rendering issue on Ubuntu
 (#13632)

Fixed incorrect clamp function argument order in PolylineGlowMaterial shader.
The original code used clamp(0.0, 1.0, glow) instead of clamp(glow, 0.0, 1.0),
which caused the alpha value to always be 1.0 regardless of the glow intensity.
This fixes the rendering issue where PolylineGlowMaterial did not display
correctly on Ubuntu systems.

Signed-off-by: zhaochen <453157936@qq.com>
---
 CHANGES.md                                                      | 1 +
 CONTRIBUTORS.md                                                 | 1 +
 .../engine/Source/Shaders/Materials/PolylineGlowMaterial.glsl   | 2 +-
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index 86aaf51407ad..1de2345c26db 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -19,6 +19,7 @@
 - Fixed incorrect JSDoc description for `offCenterFrustum` in `OrthographicFrustum` and `PerspectiveFrustum`, which was copied from `projectionMatrix` and incorrectly described the property as returning a projection matrix. [#13570](https://github.com/CesiumGS/cesium/pull/13570)
 - Auto-normalize non-unit `alignedAxis` in `BillboardCollection` instead of silently ignoring it. [#6596](https://github.com/CesiumGS/cesium/issues/6596)
 - Fixed SPZ-compressed Gaussian splat loading to read the compressed payload from the buffer view declared by `KHR_gaussian_splatting_compression_spz_2`, preventing incorrect cache reuse for assets with SPZ payloads in different buffer views. [#12847](https://github.com/CesiumGS/cesium/issues/12847)
+- Fixed incorrect parameter order when calling `clamp` in `PolylineGlowMaterial` shader, which caused the alpha value to always be 1.0 regardless of the glow intensity.
 
 ## 1.143 - 2026-07-01
 
diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index fd63904ce443..c0a6620e0ac2 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -462,3 +462,4 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to Cesiu
 - [Mustafa Senoğu](https://github.com/mmustafasenoglu)
 - [Stephan Cho](https://github.com/stephan271c)
 - [Sam Pomeroy](https://github.com/SamPomeroy)
+- [zhaochen](https://github.com/cyzhao-dad)
diff --git a/packages/engine/Source/Shaders/Materials/PolylineGlowMaterial.glsl b/packages/engine/Source/Shaders/Materials/PolylineGlowMaterial.glsl
index dbc938130486..86ae63226dab 100644
--- a/packages/engine/Source/Shaders/Materials/PolylineGlowMaterial.glsl
+++ b/packages/engine/Source/Shaders/Materials/PolylineGlowMaterial.glsl
@@ -15,7 +15,7 @@ czm_material czm_getMaterial(czm_materialInput materialInput)
 
     vec4 fragColor;
     fragColor.rgb = max(vec3(glow - 1.0 + color.rgb), color.rgb);
-    fragColor.a = clamp(0.0, 1.0, glow) * color.a;
+    fragColor.a = clamp(glow, 0.0, 1.0) * color.a;
     fragColor = czm_gammaCorrect(fragColor);
 
     material.emission = fragColor.rgb;

From 82d42d749eaaf2bd172a09a9841e057c206a812f Mon Sep 17 00:00:00 2001
From: zhaochen <453157936@qq.com>
Date: Fri, 17 Jul 2026 13:11:44 +0800
Subject: [PATCH 2/2] Trigger GitHub Actions re-run

Signed-off-by: zhaochen <453157936@qq.com>