Merge pull request #9565 from kalosma/shadowmap_fade_opt

ShadowMap fade option

CHANGES.md

@@ -1,5 +1,11 @@
 # Change Log
 
+### 1.83 - 2021-07-01
+
+##### Additions :tada:
+
+- Added `options.fadingEnabled` parameter to `ShadowMap` to control whether shadows fade out when the light source is close to the horizon. [#9565](https://github.com/CesiumGS/cesium/pull/9565)
+
 ### 1.82.1 - 2021-06-01
 
 - This is an npm only release to fix the improperly published 1.82.0.

Source/Scene/ShadowMap.js

@@ -69,6 +69,7 @@ import ShadowMapShader from "./ShadowMapShader.js";
  * @param {Boolean} [options.softShadows=false] Whether percentage-closer-filtering is enabled for producing softer shadows.
  * @param {Number} [options.darkness=0.3] The shadow darkness.
  * @param {Boolean} [options.normalOffset=true] Whether a normal bias is applied to shadows.
+ * @param {Boolean} [options.fadingEnabled=true] Whether shadows start to fade out once the light gets closer to the horizon.
  *
  * @exception {DeveloperError} Only one or four cascades are supported.
  *
@@ -117,6 +118,14 @@ function ShadowMap(options) {
   this.darkness = defaultValue(options.darkness, 0.3);
   this._darkness = this.darkness;
 
+  /**
+   * Determines whether shadows start to fade out once the light gets closer to the horizon.
+   *
+   * @type {Boolean}
+   * @default true
+   */
+  this.fadingEnabled = defaultValue(options.fadingEnabled, true);
+
   /**
    * Determines the maximum distance of the shadow map. Only applicable for cascaded shadows. Larger distances may result in lower quality shadows.
    *
@@ -1421,15 +1430,18 @@ function checkVisibility(shadowMap, frameState) {
       scratchCartesian2
     );
     var dot = Cartesian3.dot(surfaceNormal, lightDirection);
-
-    // Shadows start to fade out once the light gets closer to the horizon.
-    // At this point the globe uses vertex lighting alone to darken the surface.
-    var darknessAmount = CesiumMath.clamp(dot / 0.1, 0.0, 1.0);
-    shadowMap._darkness = CesiumMath.lerp(
-      1.0,
-      shadowMap.darkness,
-      darknessAmount
-    );
+    if (shadowMap.fadingEnabled) {
+      // Shadows start to fade out once the light gets closer to the horizon.
+      // At this point the globe uses vertex lighting alone to darken the surface.
+      var darknessAmount = CesiumMath.clamp(dot / 0.1, 0.0, 1.0);
+      shadowMap._darkness = CesiumMath.lerp(
+        1.0,
+        shadowMap.darkness,
+        darknessAmount
+      );
+    } else {
+      shadowMap._darkness = shadowMap.darkness;
+    }
 
     if (dot < 0.0) {
       shadowMap._outOfView = true;

Specs/Scene/ShadowMapSpec.js

@@ -941,6 +941,42 @@ describe(
       });
     });
 
+    it("disables shadow fading", function () {
+      box.show = true;
+      floor.show = true;
+
+      var center = new Cartesian3.fromRadians(longitude, latitude, height);
+      scene.camera.lookAt(
+        center,
+        new HeadingPitchRange(0.0, CesiumMath.toRadians(-70.0), 5.0)
+      );
+
+      // Create light camera pointing straight down
+      var lightCamera = new Camera(scene);
+      lightCamera.lookAt(center, new Cartesian3(0.0, 0.0, 1.0));
+
+      scene.shadowMap = new ShadowMap({
+        context: scene.context,
+        lightCamera: lightCamera,
+      });
+
+      // Render with light looking straight down
+      var shadowedColor = renderAndReadPixels();
+
+      // Move the light close to the horizon
+      lightCamera.lookAt(center, new Cartesian3(1.0, 0.0, 0.01));
+
+      // Render with faded shadows
+      var horizonShadowedColor = renderAndReadPixels();
+
+      // Render with unfaded shadows
+      scene.shadowMap.fadingEnabled = false;
+      renderAndCall(function (rgba) {
+        expect(horizonShadowedColor).not.toEqual(shadowedColor);
+        expect(rgba).not.toEqual(horizonShadowedColor);
+      });
+    });
+
     function depthFramebufferSupported() {
       var framebuffer = new Framebuffer({
         context: scene.context,