Add translucent tile classification

CHANGES.md

@@ -5,6 +5,7 @@
 ##### Additions :tada:
 
 - Added `Cesium3DTileset.pickPrimitive` for rendering primitives instead of the tileset during the pick pass.
+- Added support for for drawing ground primitives on translucent 3D Tiles. [#9399](https://github.com/CesiumGS/cesium/pull/9399)
 
 ### 1.79.1 - 2021-03-01
 

Source/Renderer/DrawCommand.js

@@ -43,6 +43,11 @@ function DrawCommand(options) {
   this._pickId = options.pickId;
   this._pickOnly = defaultValue(options.pickOnly, false);
 
+  this._depthForTranslucentClassification = defaultValue(
+    options.depthForTranslucentClassification,
+    false
+  );
+
   this.dirty = true;
   this.lastDirtyTime = 0;
 
@@ -513,6 +518,24 @@ Object.defineProperties(DrawCommand.prototype, {
       }
     },
   },
+  /**
+   * Whether this command should be derived to draw depth for classification of translucent primitives.
+   *
+   * @memberof DrawCommand.prototype
+   * @type {Boolean}
+   * @default false
+   */
+  depthForTranslucentClassification: {
+    get: function () {
+      return this._depthForTranslucentClassification;
+    },
+    set: function (value) {
+      if (this._depthForTranslucentClassification !== value) {
+        this._depthForTranslucentClassification = value;
+        this.dirty = true;
+      }
+    },
+  },
 });
 
 /**
@@ -549,6 +572,8 @@ DrawCommand.shallowClone = function (command, result) {
   result._receiveShadows = command._receiveShadows;
   result._pickId = command._pickId;
   result._pickOnly = command._pickOnly;
+  result._depthForTranslucentClassification =
+    command._depthForTranslucentClassification;
 
   result.dirty = true;
   result.lastDirtyTime = 0;

Source/Scene/Cesium3DTile.js

@@ -34,6 +34,7 @@ import SceneMode from "./SceneMode.js";
 import TileBoundingRegion from "./TileBoundingRegion.js";
 import TileBoundingSphere from "./TileBoundingSphere.js";
 import TileOrientedBoundingBox from "./TileOrientedBoundingBox.js";
+import Pass from "../Renderer/Pass.js";
 
 /**
  * A tile in a {@link Cesium3DTileset}.  When a tile is first created, its content is not loaded;
@@ -1611,11 +1612,21 @@ function updateClippingPlanes(tile, tileset) {
  * @private
  */
 Cesium3DTile.prototype.update = function (tileset, frameState, passOptions) {
-  var initCommandLength = frameState.commandList.length;
+  var commandStart = frameState.commandList.length;
+
   updateClippingPlanes(this, tileset);
   applyDebugSettings(this, tileset, frameState, passOptions);
   updateContent(this, tileset, frameState);
-  this._commandsLength = frameState.commandList.length - initCommandLength;
+
+  var commandEnd = frameState.commandList.length;
+  var commandsLength = commandEnd - commandStart;
+  this._commandsLength = commandsLength;
+
+  for (var i = 0; i < commandsLength; ++i) {
+    var command = frameState.commandList[commandStart + i];
+    var translucent = command.pass === Pass.TRANSLUCENT;
+    command.depthForTranslucentClassification = translucent;
+  }
 
   this.clippingPlanesDirty = false; // reset after content update
 };

Source/Scene/Scene.js

@@ -2658,6 +2658,28 @@ function executeCommands(scene, passState) {
       invertClassification
     );
 
+    // Classification for translucent 3D Tiles
+    var has3DTilesClassificationCommands =
+      frustumCommands.indices[Pass.CESIUM_3D_TILE_CLASSIFICATION] > 0;
+    if (
+      has3DTilesClassificationCommands &&
+      view.translucentTileClassification.isSupported()
+    ) {
+      view.translucentTileClassification.executeTranslucentCommands(
+        scene,
+        executeCommand,
+        passState,
+        commands,
+        globeDepth.framebuffer
+      );
+      view.translucentTileClassification.executeClassificationCommands(
+        scene,
+        executeCommand,
+        passState,
+        frustumCommands
+      );
+    }
+
     if (
       context.depthTexture &&
       scene.useDepthPicking &&
@@ -3439,6 +3461,13 @@ function updateAndClearFramebuffers(scene, passState, clearColor) {
     environmentState.useOIT = oit.isSupported();
   }
 
+  if (
+    useGlobeDepthFramebuffer &&
+    view.translucentTileClassification.isSupported()
+  ) {
+    view.translucentTileClassification.clear(context, passState);
+  }
+
   var postProcess = scene.postProcessStages;
   var usePostProcess = (environmentState.usePostProcess =
     !picking &&
@@ -3545,6 +3574,14 @@ Scene.prototype.resolveFramebuffers = function (passState) {
     view.oit.execute(context, passState);
   }
 
+  var translucentTileClassification = view.translucentTileClassification;
+  if (
+    translucentTileClassification.hasTranslucentDepth &&
+    translucentTileClassification.isSupported()
+  ) {
+    translucentTileClassification.execute(this, passState);
+  }
+
   if (usePostProcess) {
     var inputFramebuffer = sceneFramebuffer;
     if (useGlobeDepthFramebuffer && !useOIT) {