Distance-based Gaussian weighting for Ambient Occlusion

Apps/Sandcastle/gallery/Ambient Occlusion.html

@@ -62,38 +62,38 @@
             </td>
           </tr>
           <tr>
-            <td>Step Size</td>
+            <td>Step Count</td>
             <td>
               <input
                 type="range"
                 min="1"
-                max="10"
-                step="0.01"
-                data-bind="value: stepSize, valueUpdate: 'input'"
+                max="64"
+                step="1"
+                data-bind="value: stepCount, valueUpdate: 'input'"
               />
             </td>
           </tr>
           <tr>
-            <td>Bias</td>
+            <td>Direction Count</td>
             <td>
               <input
                 type="range"
-                min="0"
-                max="1"
-                step="0.01"
-                data-bind="value: bias, valueUpdate: 'input'"
+                min="1"
+                max="16"
+                step="1"
+                data-bind="value: directionCount, valueUpdate: 'input'"
               />
             </td>
           </tr>
           <tr>
-            <td>Blur Step Size</td>
+            <td>Bias</td>
             <td>
               <input
                 type="range"
                 min="0"
-                max="4"
+                max="1"
                 step="0.01"
-                data-bind="value: blurStepSize, valueUpdate: 'input'"
+                data-bind="value: bias, valueUpdate: 'input'"
               />
             </td>
           </tr>
@@ -106,7 +106,11 @@
         //Sandcastle_Begin
         const viewer = new Cesium.Viewer("cesiumContainer");
 
-        viewer.clock.currentTime = Cesium.JulianDate.fromIso8601("2022-08-01T00:00:00Z");
+        const { canvas, camera, clock, scene } = viewer;
+        camera.frustum.near = 1.0;
+        scene.debugShowFramesPerSecond = true;
+
+        clock.currentTime = Cesium.JulianDate.fromIso8601("2022-08-01T00:00:00Z");
 
         if (!Cesium.PostProcessStageLibrary.isAmbientOcclusionSupported(viewer.scene)) {
           window.alert(
@@ -119,9 +123,9 @@
           ambientOcclusionOnly: false,
           intensity: 3.0,
           bias: 0.1,
-          lengthCap: 0.03,
-          stepSize: 1.0,
-          blurStepSize: 0.86,
+          lengthCap: 0.26,
+          directionCount: 8,
+          stepCount: 32,
         };
 
         Cesium.knockout.track(viewModel);
@@ -134,7 +138,7 @@
         }
 
         function updatePostProcess() {
-          const ambientOcclusion = viewer.scene.postProcessStages.ambientOcclusion;
+          const ambientOcclusion = scene.postProcessStages.ambientOcclusion;
           ambientOcclusion.enabled =
             Boolean(viewModel.show) || Boolean(viewModel.ambientOcclusionOnly);
           ambientOcclusion.uniforms.ambientOcclusionOnly = Boolean(
@@ -143,12 +147,11 @@
           ambientOcclusion.uniforms.intensity = Number(viewModel.intensity);
           ambientOcclusion.uniforms.bias = Number(viewModel.bias);
           ambientOcclusion.uniforms.lengthCap = Number(viewModel.lengthCap);
-          ambientOcclusion.uniforms.stepSize = Number(viewModel.stepSize);
-          ambientOcclusion.uniforms.blurStepSize = Number(viewModel.blurStepSize);
+          ambientOcclusion.uniforms.directionCount = Number(viewModel.directionCount);
+          ambientOcclusion.uniforms.stepCount = Number(viewModel.stepCount);
         }
         updatePostProcess();
 
-        const camera = viewer.scene.camera;
         camera.position = new Cesium.Cartesian3(
           1234127.2294710164,
           -5086011.666443127,
@@ -173,7 +176,7 @@
         try {
           // Power Plant design model provided by Bentley Systems
           const tileset = await Cesium.Cesium3DTileset.fromIonAssetId(2464651);
-          viewer.scene.primitives.add(tileset);
+          scene.primitives.add(tileset);
         } catch (error) {
           console.log(`Error loading tileset: ${error}`);
         } //Sandcastle_End

CHANGES.md

@@ -18,6 +18,7 @@
 ##### Breaking Changes :mega:
 
 - `Rectangle.validate` has been removed.
+- `PostProcessStageCollection.ambientOcclusion` has been updated with a new algorithm to provide better results at all scales, with tunable performance cost. To approximate the appearance and performance of the old algorithm, set the following values for `scene.postProcessStages.ambientOcclusion.uniforms`: `{ lengthCap: 0.02, directionCount: 6, stepCount: 8 }`. For best results at long distances, consider setting `Viewer.camera.frustum.near` to `1.0` or more, to improve precision in the depth buffer.
 
 ##### Fixes :wrench:
 

packages/engine/Source/Scene/PostProcessStage.js

@@ -94,9 +94,16 @@ import PostProcessStageSampleMode from "./PostProcessStageSampleMode.js";
 function PostProcessStage(options) {
   options = defaultValue(options, defaultValue.EMPTY_OBJECT);
   const {
+    name = createGuid(),
     fragmentShader,
+    uniforms,
     textureScale = 1.0,
+    forcePowerOfTwo = false,
+    sampleMode = PostProcessStageSampleMode.NEAREST,
     pixelFormat = PixelFormat.RGBA,
+    pixelDatatype = PixelDatatype.UNSIGNED_BYTE,
+    clearColor = Color.BLACK,
+    scissorRectangle,
   } = options;
 
   //>>includeStart('debug', pragmas.debug);
@@ -113,19 +120,13 @@ function PostProcessStage(options) {
   //>>includeEnd('debug');
 
   this._fragmentShader = fragmentShader;
-  this._uniforms = options.uniforms;
+  this._uniforms = uniforms;
   this._textureScale = textureScale;
-  this._forcePowerOfTwo = defaultValue(options.forcePowerOfTwo, false);
-  this._sampleMode = defaultValue(
-    options.sampleMode,
-    PostProcessStageSampleMode.NEAREST,
-  );
+  this._forcePowerOfTwo = forcePowerOfTwo;
+  this._sampleMode = sampleMode;
   this._pixelFormat = pixelFormat;
-  this._pixelDatatype = defaultValue(
-    options.pixelDatatype,
-    PixelDatatype.UNSIGNED_BYTE,
-  );
-  this._clearColor = defaultValue(options.clearColor, Color.BLACK);
+  this._pixelDatatype = pixelDatatype;
+  this._clearColor = clearColor;
 
   this._uniformMap = undefined;
   this._command = undefined;
@@ -143,18 +144,14 @@ function PostProcessStage(options) {
   const passState = new PassState();
   passState.scissorTest = {
     enabled: true,
-    rectangle: defined(options.scissorRectangle)
-      ? BoundingRectangle.clone(options.scissorRectangle)
+    rectangle: defined(scissorRectangle)
+      ? BoundingRectangle.clone(scissorRectangle)
       : new BoundingRectangle(),
   };
   this._passState = passState;
 
   this._ready = false;
 
-  let name = options.name;
-  if (!defined(name)) {
-    name = createGuid();
-  }
   this._name = name;
 
   this._logDepthChanged = undefined;

packages/engine/Source/Scene/PostProcessStageCollection.js

@@ -155,32 +155,20 @@ Object.defineProperties(PostProcessStageCollection.prototype, {
    * surface receives light and regardless of the light's position.
    * </p>
    * <p>
-   * The uniforms have the following properties: <code>intensity</code>, <code>bias</code>, <code>lengthCap</code>,
-   * <code>stepSize</code>, <code>frustumLength</code>, <code>ambientOcclusionOnly</code>,
-   * <code>delta</code>, <code>sigma</code>, and <code>blurStepSize</code>.
-   * </p>
+   * The uniforms have the following properties:
    * <ul>
    * <li><code>intensity</code> is a scalar value used to lighten or darken the shadows exponentially. Higher values make the shadows darker. The default value is <code>3.0</code>.</li>
-   *
    * <li><code>bias</code> is a scalar value representing an angle in radians. If the dot product between the normal of the sample and the vector to the camera is less than this value,
    * sampling stops in the current direction. This is used to remove shadows from near planar edges. The default value is <code>0.1</code>.</li>
-   *
    * <li><code>lengthCap</code> is a scalar value representing a length in meters. If the distance from the current sample to first sample is greater than this value,
    * sampling stops in the current direction. The default value is <code>0.26</code>.</li>
-   *
-   * <li><code>stepSize</code> is a scalar value indicating the distance to the next texel sample in the current direction. The default value is <code>1.95</code>.</li>
-   *
-   * <li><code>frustumLength</code> is a scalar value in meters. If the current fragment has a distance from the camera greater than this value, ambient occlusion is not computed for the fragment.
-   * The default value is <code>1000.0</code>.</li>
-   *
+   * <li><code>directionCount</code> is the number of directions along which the ray marching will search for occluders. The default value is <code>8</code>.</li>
+   * <li><code>stepCount</code> is the number of steps the ray marching will take along each direction. The default value is <code>32</code>.</li>
+   * <li><code>randomTexture</code> is a texture where the red channel is a random value in [0.0, 1.0]. The default value is <code>undefined</code>. This texture needs to be set.</li>
    * <li><code>ambientOcclusionOnly</code> is a boolean value. When <code>true</code>, only the shadows generated are written to the output. When <code>false</code>, the input texture is modulated
    * with the ambient occlusion. This is a useful debug option for seeing the effects of changing the uniform values. The default value is <code>false</code>.</li>
    * </ul>
    * <p>
-   * <code>delta</code>, <code>sigma</code>, and <code>blurStepSize</code> are the same properties as {@link PostProcessStageLibrary#createBlurStage}.
-   * The blur is applied to the shadows generated from the image to make them smoother.
-   * </p>
-   * <p>
    * When enabled, this stage will execute before all others.
    * </p>
    *

packages/engine/Source/Scene/PostProcessStageLibrary.js

@@ -476,27 +476,19 @@ PostProcessStageLibrary.createBloomStage = function () {
  * surface receives light and regardless of the light's position.
  * </p>
  * <p>
- * The uniforms have the following properties: <code>intensity</code>, <code>bias</code>, <code>lengthCap</code>,
- * <code>stepSize</code>, <code>frustumLength</code>, <code>randomTexture</code>, <code>ambientOcclusionOnly</code>,
- * <code>delta</code>, <code>sigma</code>, and <code>blurStepSize</code>.
- * </p>
+ * The uniforms have the following properties:
  * <ul>
  * <li><code>intensity</code> is a scalar value used to lighten or darken the shadows exponentially. Higher values make the shadows darker. The default value is <code>3.0</code>.</li>
  * <li><code>bias</code> is a scalar value representing an angle in radians. If the dot product between the normal of the sample and the vector to the camera is less than this value,
  * sampling stops in the current direction. This is used to remove shadows from near planar edges. The default value is <code>0.1</code>.</li>
  * <li><code>lengthCap</code> is a scalar value representing a length in meters. If the distance from the current sample to first sample is greater than this value,
  * sampling stops in the current direction. The default value is <code>0.26</code>.</li>
- * <li><code>stepSize</code> is a scalar value indicating the distance to the next texel sample in the current direction. The default value is <code>1.95</code>.</li>
- * <li><code>frustumLength</code> is a scalar value in meters. If the current fragment has a distance from the camera greater than this value, ambient occlusion is not computed for the fragment.
- * The default value is <code>1000.0</code>.</li>
+ * <li><code>directionCount</code> is the number of directions along which the ray marching will search for occluders. The default value is <code>8</code>.</li>
+ * <li><code>stepCount</code> is the number of steps the ray marching will take along each direction. The default value is <code>32</code>.</li>
  * <li><code>randomTexture</code> is a texture where the red channel is a random value in [0.0, 1.0]. The default value is <code>undefined</code>. This texture needs to be set.</li>
  * <li><code>ambientOcclusionOnly</code> is a boolean value. When <code>true</code>, only the shadows generated are written to the output. When <code>false</code>, the input texture is modulated
  * with the ambient occlusion. This is a useful debug option for seeing the effects of changing the uniform values. The default value is <code>false</code>.</li>
  * </ul>
- * <p>
- * <code>delta</code>, <code>sigma</code>, and <code>blurStepSize</code> are the same properties as {@link PostProcessStageLibrary#createBlurStage}.
- * The blur is applied to the shadows generated from the image to make them smoother.
- * </p>
  * @return {PostProcessStageComposite} A post-process stage that applies an ambient occlusion effect.
  *
  * @private
@@ -509,24 +501,18 @@ PostProcessStageLibrary.createAmbientOcclusionStage = function () {
       intensity: 3.0,
       bias: 0.1,
       lengthCap: 0.26,
-      stepSize: 1.95,
-      frustumLength: 1000.0,
+      directionCount: 8,
+      stepCount: 32,
       randomTexture: undefined,
     },
   });
-  const blur = createBlur("czm_ambient_occlusion_blur");
-  blur.uniforms.stepSize = 0.86;
-  const generateAndBlur = new PostProcessStageComposite({
-    name: "czm_ambient_occlusion_generate_blur",
-    stages: [generate, blur],
-  });
 
   const ambientOcclusionModulate = new PostProcessStage({
     name: "czm_ambient_occlusion_composite",
     fragmentShader: AmbientOcclusionModulate,
     uniforms: {
       ambientOcclusionOnly: false,
-      ambientOcclusionTexture: generateAndBlur.name,
+      ambientOcclusionTexture: generate.name,
     },
   });
 
@@ -556,20 +542,20 @@ PostProcessStageLibrary.createAmbientOcclusionStage = function () {
         generate.uniforms.lengthCap = value;
       },
     },
-    stepSize: {
+    directionCount: {
       get: function () {
-        return generate.uniforms.stepSize;
+        return generate.uniforms.directionCount;
       },
       set: function (value) {
-        generate.uniforms.stepSize = value;
+        generate.uniforms.directionCount = value;
       },
     },
-    frustumLength: {
+    stepCount: {
       get: function () {
-        return generate.uniforms.frustumLength;
+        return generate.uniforms.stepCount;
       },
       set: function (value) {
-        generate.uniforms.frustumLength = value;
+        generate.uniforms.stepCount = value;
       },
     },
     randomTexture: {
@@ -580,30 +566,6 @@ PostProcessStageLibrary.createAmbientOcclusionStage = function () {
         generate.uniforms.randomTexture = value;
       },
     },
-    delta: {
-      get: function () {
-        return blur.uniforms.delta;
-      },
-      set: function (value) {
-        blur.uniforms.delta = value;
-      },
-    },
-    sigma: {
-      get: function () {
-        return blur.uniforms.sigma;
-      },
-      set: function (value) {
-        blur.uniforms.sigma = value;
-      },
-    },
-    blurStepSize: {
-      get: function () {
-        return blur.uniforms.stepSize;
-      },
-      set: function (value) {
-        blur.uniforms.stepSize = value;
-      },
-    },
     ambientOcclusionOnly: {
       get: function () {
         return ambientOcclusionModulate.uniforms.ambientOcclusionOnly;
@@ -616,7 +578,7 @@ PostProcessStageLibrary.createAmbientOcclusionStage = function () {
 
   return new PostProcessStageComposite({
     name: "czm_ambient_occlusion",
-    stages: [generateAndBlur, ambientOcclusionModulate],
+    stages: [generate, ambientOcclusionModulate],
     inputPreviousStageTexture: false,
     uniforms: uniforms,
   });

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

@@ -4,7 +4,7 @@ float czm_reverseLogDepth(float logZ)
     float near = czm_currentFrustum.x;
     float far = czm_currentFrustum.y;
     float log2Depth = logZ * czm_log2FarDepthFromNearPlusOne;
-    float depthFromNear = pow(2.0, log2Depth) - 1.0;
+    float depthFromNear = exp2(log2Depth) - 1.0;
     return far * (1.0 - near / (depthFromNear + near)) / (far - near);
 #endif
     return logZ;

packages/engine/Source/Shaders/ConvolveSpecularMapFS.glsl

@@ -62,7 +62,7 @@ void main() {
 
             float NdotL = max(dot(V, L), 0.0);
             if (NdotL > 0.0) {
-                color += vec4(texture(u_radianceTexture, L).rgb, 1.0) * NdotL;
+                color += vec4(czm_textureCube(u_radianceTexture, L).rgb, 1.0) * NdotL;
                 weight += NdotL;
             }
         }