Merge pull request #5367 from klingerj/billboard-alignment-fix

Fixed the billboard alignedaxis issue.
CesiumGS · May 25, 2017 · 6eb0439 · 6eb0439
2 parents 8905593 + 790067b
commit 6eb0439
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diff --git a/CHANGES.md b/CHANGES.md
@@ -18,6 +18,7 @@ Change Log
 * Updated documentation for Quaternion.fromHeadingPitchRoll [#5264](https://github.com/AnalyticalGraphicsInc/cesium/issues/5264)
 * Fixed an issue where using the depth fail material for polylines would cause a crash in Edge. [#5359](https://github.com/AnalyticalGraphicsInc/cesium/pull/5359)
 * Fixed a crash where EllipsoidGeometry and EllipsoidOutlineGeometry were given floating point values when expecting integers. [#5260](https://github.com/AnalyticalGraphicsInc/cesium/issues/5260)
+* Fixed an issue where billboards were not properly aligned. [#2487](https://github.com/AnalyticalGraphicsInc/cesium/issues/2487)
 
 ### 1.33 - 2017-05-01
 

diff --git a/Source/Shaders/BillboardCollectionVS.glsl b/Source/Shaders/BillboardCollectionVS.glsl
@@ -51,11 +51,9 @@ vec4 computePositionWindowCoordinates(vec4 positionEC, vec2 imageSize, float sca
         float angle = rotation;
         if (validAlignedAxis)
         {
-            vec3 pos = positionEC.xyz + czm_encodedCameraPositionMCHigh + czm_encodedCameraPositionMCLow;
-            vec3 normal = normalize(cross(alignedAxis, pos));
-            vec4 tangent = vec4(normalize(cross(pos, normal)), 0.0);
-            tangent = czm_modelViewProjection * tangent;
-            angle += sign(-tangent.x) * acos(tangent.y / length(tangent.xy));
+            vec4 projectedAlignedAxis = czm_modelViewProjection * vec4(alignedAxis, 0.0);
+            angle += sign(-projectedAlignedAxis.x) * acos( sign(projectedAlignedAxis.y) * (projectedAlignedAxis.y * projectedAlignedAxis.y) /
+                    (projectedAlignedAxis.x * projectedAlignedAxis.x + projectedAlignedAxis.y * projectedAlignedAxis.y) );
         }
 
         float cosTheta = cos(angle);