add ignoreBlackPixels option to czm_applyHSBShift

packages/engine/Source/Shaders/Builtin/Functions/applyHSBShift.glsl

@@ -3,18 +3,29 @@
  *
  * @param {vec3} rgb The color in RGB space.
  * @param {vec3} hsbShift The amount to shift each component. The xyz components correspond to hue, saturation, and brightness. Shifting the hue by +/- 1.0 corresponds to shifting the hue by a full cycle. Saturation and brightness are clamped between 0 and 1 after the adjustment
+ * @param {bool} ignoreBlackPixels If true, black pixels will be unchanged. This is necessary in some shaders such as atmosphere-related effects.
  *
  * @return {vec3} The RGB color after shifting in HSB space and clamping saturation and brightness to a valid range.
  */
-vec3 czm_applyHSBShift(vec3 rgb, vec3 hsbShift) {
+vec3 czm_applyHSBShift(vec3 rgb, vec3 hsbShift, bool ignoreBlackPixels) {
     // Convert rgb color to hsb
     vec3 hsb = czm_RGBToHSB(rgb);
 
     // Perform hsb shift
     // Hue cycles around so no clamp is needed.
     hsb.x += hsbShift.x; // hue
     hsb.y = clamp(hsb.y + hsbShift.y, 0.0, 1.0); // saturation
-    hsb.z = clamp(hsb.z + hsbShift.z, 0.0, 1.0); // brightness
+
+    // brightness
+    //
+    // Some shaders such as atmosphere-related effects need to leave black
+    // pixels unchanged
+    if (ignoreBlackPixels) {
+        hsb.z = hsb.z > czm_epsilon7 ? hsb.z + hsbShift.z : 0.0;
+    } else {
+        hsb.z = hsb.z + hsbShift.z;
+    }
+    hsb.z = clamp(hsb.z, 0.0, 1.0);
 
     // Convert shifted hsb back to rgb
     return czm_HSBToRGB(hsb);

packages/engine/Source/Shaders/GlobeFS.glsl

@@ -268,20 +268,6 @@ vec4 sampleAndBlend(
     return vec4(outColor, max(outAlpha, 0.0));
 }
 
-vec3 colorCorrect(vec3 rgb) {
-#ifdef COLOR_CORRECT
-    // Convert rgb color to hsb
-    vec3 hsb = czm_RGBToHSB(rgb);
-    // Perform hsb shift
-    hsb.x += u_hsbShift.x; // hue
-    hsb.y = clamp(hsb.y + u_hsbShift.y, 0.0, 1.0); // saturation
-    hsb.z = hsb.z > czm_epsilon7 ? hsb.z + u_hsbShift.z : 0.0; // brightness
-    // Convert shifted hsb back to rgb
-    rgb = czm_HSBToRGB(hsb);
-#endif
-    return rgb;
-}
-
 vec4 computeDayColor(vec4 initialColor, vec3 textureCoordinates, float nightBlend);
 vec4 computeWaterColor(vec3 positionEyeCoordinates, vec2 textureCoordinates, mat3 enuToEye, vec4 imageryColor, float specularMapValue, float fade);
 
@@ -473,8 +459,9 @@ void main()
         #endif
 
         #ifdef COLOR_CORRECT
-            rayleighColor = czm_applyHSBShift(rayleighColor, u_hsbShift);
-            mieColor = czm_applyHSBShift(mieColor, u_hsbShift);
+            const bool ignoreBlackPixels = true;
+            rayleighColor = czm_applyHSBShift(rayleighColor, u_hsbShift, ignoreBlackPixels);
+            mieColor = czm_applyHSBShift(mieColor, u_hsbShift, ignoreBlackPixels);
         #endif
 
         vec4 groundAtmosphereColor = computeAtmosphereColor(positionWC, lightDirection, rayleighColor, mieColor, opacity);

packages/engine/Source/Shaders/Model/AtmosphereStageFS.glsl

@@ -96,8 +96,9 @@ void atmosphereStage(inout vec4 color, in ProcessedAttributes attributes) {
     }
 
     //color correct rayleigh and mie colors
-    rayleighColor = czm_applyHSBShift(rayleighColor, czm_atmosphereHsbShift);
-    mieColor = czm_applyHSBShift(mieColor, czm_atmosphereHsbShift);
+    const bool ignoreBlackPixels = true;
+    rayleighColor = czm_applyHSBShift(rayleighColor, czm_atmosphereHsbShift, ignoreBlackPixels);
+    mieColor = czm_applyHSBShift(mieColor, czm_atmosphereHsbShift, ignoreBlackPixels);
 
     vec4 groundAtmosphereColor = czm_computeAtmosphereColor(positionWC, lightDirection, rayleighColor, mieColor, opacity);