@@ -102,16 +102,58 @@ void calculateRayScatteringFromGround(in vec3 positionWC, in vec3 ray, in float
102102 startOffset = depth* scale(startAngle);
103103}
104104
105- void calculateMieColorAndRayleighColor( vec3 positionWC , vec3 outerPosition , vec3 lightDirection, bool intersectsEllipsoid, out vec3 mieColor, out vec3 rayleighColor )
105+ czm_raySegment rayEllipsoidIntersection(czm_ray ray , vec3 ellipsoid_center , vec3 ellipsoid_inverseRadii )
106106{
107- float cameraHeight = length (positionWC);
107+ vec3 o = ellipsoid_inverseRadii * (czm_inverseModelView * vec4 (ray.origin, 1.0 )).xyz;
108+ vec3 d = ellipsoid_inverseRadii * (czm_inverseModelView * vec4 (ray.direction, 0.0 )).xyz;
109+
110+ float a = dot (d, d);
111+ float b = dot (d, o);
112+ float c = dot (o, o) - 1.0 ;
113+ float discriminant = b * b - a * c;
114+ if (discriminant < 0.0 )
115+ {
116+ return czm_emptyRaySegment;
117+ }
118+ discriminant = sqrt (discriminant);
119+ float t1 = (- b + (- discriminant)) / a;
120+ float t2 = (- b + (discriminant)) / a;
121+
122+ if (t1 < 0.0 && t2 < 0.0 )
123+ {
124+ return czm_emptyRaySegment;
125+ }
126+
127+ if (t1 < 0.0 && t2 >= 0.0 )
128+ {
129+ t1 = 0.0 ;
130+ }
131+
132+ return czm_raySegment(t1, t2);
133+ }
134+
135+ void calculateMieColorAndRayleighColor(vec3 outerPositionWC, float ellipsoidScaleFactor, out vec3 mieColor, out vec3 rayleighColor)
136+ {
137+ vec3 directionWC = normalize (outerPositionWC - czm_viewerPositionWC);
138+ vec3 directionEC = czm_viewRotation * directionWC;
139+ czm_ray viewRay = czm_ray(vec3 (0.0 ), directionEC);
140+ czm_raySegment raySegment = rayEllipsoidIntersection(viewRay, vec3 (czm_view[3 ]), czm_ellipsoidInverseRadii * ellipsoidScaleFactor);
141+ bool intersectsEllipsoid = raySegment.start >= 0.0 ;
142+
143+ vec3 startPositionWC = czm_viewerPositionWC;
144+ if (intersectsEllipsoid)
145+ {
146+ startPositionWC = czm_viewerPositionWC + raySegment.stop * directionWC;
147+ }
148+
149+ vec3 lightDirection = getLightDirection(startPositionWC);
108150
109151 // Unpack attributes
110152 float outerRadius = u_radiiAndDynamicAtmosphereColor.x;
111153 float innerRadius = u_radiiAndDynamicAtmosphereColor.y;
112154
113155 // Get the ray from the start position to the outer position and its length (which is the far point of the ray passing through the atmosphere)
114- vec3 ray = outerPosition - positionWC ;
156+ vec3 ray = outerPositionWC - startPositionWC ;
115157 float far = length (ray);
116158 ray /= far;
117159 float atmosphereScale = 1.0 / (outerRadius - innerRadius);
@@ -122,14 +164,14 @@ void calculateMieColorAndRayleighColor(vec3 positionWC, vec3 outerPosition, vec3
122164#ifdef SKY_FROM_SPACE
123165 if (intersectsEllipsoid)
124166 {
125- calculateRayScatteringFromGround(positionWC , ray, atmosphereScale, innerRadius, start, startOffset);
167+ calculateRayScatteringFromGround(startPositionWC , ray, atmosphereScale, innerRadius, start, startOffset);
126168 }
127169 else
128170 {
129- calculateRayScatteringFromSpace(positionWC , ray, outerRadius, far, start, startOffset);
171+ calculateRayScatteringFromSpace(startPositionWC , ray, outerRadius, far, start, startOffset);
130172 }
131173#else
132- calculateRayScatteringFromGround(positionWC , ray, atmosphereScale, innerRadius, start, startOffset);
174+ calculateRayScatteringFromGround(startPositionWC , ray, atmosphereScale, innerRadius, start, startOffset);
133175#endif
134176
135177 // Initialize the scattering loop variables
@@ -167,12 +209,6 @@ vec4 calculateFinalColor(vec3 positionWC, vec3 toCamera, vec3 lightDirection, ve
167209
168210 vec3 rgb = rayleighPhase * rayleighColor + miePhase * mieColor;
169211
170- if (rgb.b > 1000000.0 )
171- {
172- // Discard colors that exceed some large number value to prevent against NaN's from the exponent calculation below
173- return vec4 (0.0 );
174- }
175-
176212 const float exposure = 2.0 ;
177213 vec3 rgbExposure = vec3 (1.0 ) - exp (- exposure * rgb);
178214
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