Merge pull request #3032 from AnalyticalGraphicsInc/sky-bug

Fix disappearing terrain and sky
CesiumGS · Sep 16, 2015 · 0836231 · 0836231
2 parents 18a80ae + 174ff31
commit 0836231
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Showing 5 changed files with 45 additions and 9 deletions.
diff --git a/CHANGES.md b/CHANGES.md
@@ -16,6 +16,8 @@ Change Log
 * Fixed a bug that prevented `setView` from working across all scene modes.
 * Fixed a bug that caused `camera.positionWC` to occasionally return the incorrect value.
 * Added a workaround for Chrome 45, where the first character in a label with a small font size would not appear. [#3011](https://github.com/AnalyticalGraphicsInc/cesium/pull/3011)
+* Fixed issues causing the terrain and sky to disappear when the camera is near the surface. [#2415](https://github.com/AnalyticalGraphicsInc/cesium/issues/2415) and [#2271](https://github.com/AnalyticalGraphicsInc/cesium/issues/2271)
+* Changed the `ScreenSpaceCameraController.minimumZoomDistance` default from `20.0` to `1.0`.
 
 ### 1.13 - 2015-09-01
 

diff --git a/Source/Core/EllipsoidalOccluder.js b/Source/Core/EllipsoidalOccluder.js
@@ -129,6 +129,11 @@ define([
      * occluder.isScaledSpacePointVisible(scaledSpacePoint); //returns true
      */
     EllipsoidalOccluder.prototype.isScaledSpacePointVisible = function(occludeeScaledSpacePosition) {
+        // Disable occlusion culling when the viewer is under the ellipsoid to avoid false occulsion.
+        if (this._distanceToLimbInScaledSpaceSquared < 0.0) {
+            return true;
+        }
+
         // See http://cesiumjs.org/2013/04/25/Horizon-culling/
         var cv = this._cameraPositionInScaledSpace;
         var vhMagnitudeSquared = this._distanceToLimbInScaledSpaceSquared;

diff --git a/Source/Scene/ScreenSpaceCameraController.js b/Source/Scene/ScreenSpaceCameraController.js
@@ -155,7 +155,7 @@ define([
          * @type {Number}
          * @default 20.0
          */
-        this.minimumZoomDistance = 20.0;
+        this.minimumZoomDistance = 1.0;
         /**
          * The maximum magnitude, in meters, of the camera position when zooming. Defaults to positive infinity.
          * @type {Number}

diff --git a/Source/Shaders/SkyAtmosphereFS.glsl b/Source/Shaders/SkyAtmosphereFS.glsl
@@ -36,6 +36,9 @@
 const float g = -0.95;
 const float g2 = g * g;
 
+uniform float fCameraHeight;
+uniform float fInnerRadius;
+
 varying vec3 v_rayleighColor;
 varying vec3 v_mieColor;
 varying vec3 v_toCamera;
@@ -49,9 +52,35 @@ void main (void)
     vec3 direction = normalize(v_positionEC);
     czm_ray ray = czm_ray(vec3(0.0), direction);
 
-    czm_raySegment intersection = czm_rayEllipsoidIntersectionInterval(ray, ellipsoid);
-    if (!czm_isEmpty(intersection)) {
-        discard;
+    if (fCameraHeight > fInnerRadius) {
+	    czm_raySegment intersection = czm_rayEllipsoidIntersectionInterval(ray, ellipsoid);
+	    if (!czm_isEmpty(intersection)) {
+	        discard;
+	    }
+	} else {
+	    // The ellipsoid test above will discard fragments when the ray origin is
+	    // inside the ellipsoid.
+	    vec3 radii = ellipsoid.radii;
+	    float maxRadius = max(radii.x, max(radii.y, radii.z));
+	    vec3 ellipsoidCenter = czm_modelView[3].xyz;
+
+	    float t1 = -1.0;
+	    float t2 = -1.0;
+
+	    float b = -2.0 * dot(direction, ellipsoidCenter);
+	    float c = dot(ellipsoidCenter, ellipsoidCenter) - maxRadius * maxRadius;
+
+	    float discriminant = b * b - 4.0 * c;
+	    if (discriminant >= 0.0) {
+	        t1 = (-b - sqrt(discriminant)) * 0.5;
+	        t2 = (-b + sqrt(discriminant)) * 0.5;
+	    }
+
+	    if (t1 < 0.0 && t2 < 0.0) {
+	        // The ray through the fragment intersected the sphere approximating
+	        // the ellipsoid behind the ray origin.
+	        discard;
+	    }
     }
 
     // Extra normalize added for Android

diff --git a/Specs/Scene/ScreenSpaceCameraControllerSpec.js b/Specs/Scene/ScreenSpaceCameraControllerSpec.js
@@ -301,7 +301,7 @@ defineSuite([
         moveMouse(MouseButtons.RIGHT, startPosition, endPosition);
         updateController();
         expect(position.x).toEqual(camera.position.x);
-        expect(position.y).toBeLessThan(camera.position.y);
+        expect(position.y).toEqual(camera.position.y);
         expect(position.z).toEqual(camera.position.z);
         expect(frustumDiff).toBeGreaterThan(camera.frustum.right - camera.frustum.left);
     });
@@ -364,7 +364,7 @@ defineSuite([
         moveMouse(MouseButtons.RIGHT, startPosition, endPosition);
         updateController();
         expect(position.x).toEqual(camera.position.x);
-        expect(position.y).toBeLessThan(camera.position.y);
+        expect(position.y).toEqual(camera.position.y);
         expect(position.z).toEqual(camera.position.z);
         expect(frustumDiff).toBeGreaterThan(camera.frustum.right - camera.frustum.left);
     });
@@ -1051,7 +1051,7 @@ defineSuite([
         updateController();
 
         camera.setView({
-            position : Cartesian3.fromDegrees(-72.0, 40.0, 1.0)
+            position : Cartesian3.fromDegrees(-72.0, 40.0, -10.0)
         });
 
         updateController();
@@ -1067,7 +1067,7 @@ defineSuite([
         updateController();
 
         camera.setView({
-            position : Cartesian3.fromDegrees(-72.0, 40.0, 1.0)
+            position : Cartesian3.fromDegrees(-72.0, 40.0, -10.0)
         });
 
         updateController();
@@ -1098,7 +1098,7 @@ defineSuite([
 
         updateController();
 
-        expect(camera.positionWC.x).toBeGreaterThanOrEqualTo(controller.minimumZoomDistance);
+        expect(camera.positionWC.x).toEqualEpsilon(controller.minimumZoomDistance, CesiumMath.EPSILON8);
     });
 
     it('is destroyed', function() {