Fix clipping plane issue with child tiles with transforms

CHANGES.md

@@ -37,6 +37,7 @@ Change Log
 * Allowed Bing Maps servers with a subpath (instead of being at the root) to work correctly. [#6597](https://github.com/AnalyticalGraphicsInc/cesium/pull/6597)
 * Fixed polygon outline when using `perPositionHeight` and `extrudedHeight`. [#6595](https://github.com/AnalyticalGraphicsInc/cesium/issues/6595)
 * Fixed broken links in documentation of `createTileMapServiceImageryProvider`. [#5818](https://github.com/AnalyticalGraphicsInc/cesium/issues/5818)
+* Fixed bug where child tiles with transforms were not being clipped correctly. [#6600](https://github.com/AnalyticalGraphicsInc/cesium/issues/6600)
 
 ### 1.45 - 2018-05-01
 

Source/Scene/Batched3DModel3DTileContent.js

@@ -9,6 +9,7 @@ define([
         '../Core/FeatureDetection',
         '../Core/getBaseUri',
         '../Core/getStringFromTypedArray',
+        '../Core/Matrix4',
         '../Core/RequestType',
         '../Core/RuntimeError',
         '../Renderer/Pass',
@@ -29,6 +30,7 @@ define([
         FeatureDetection,
         getBaseUri,
         getStringFromTypedArray,
+        Matrix4,
         RequestType,
         RuntimeError,
         Pass,
@@ -439,6 +441,7 @@ define([
         this._batchTable.applyStyle(frameState, style);
     };
 
+    var scratchClippingPlaneMatrix = new Matrix4();
     Batched3DModel3DTileContent.prototype.update = function(tileset, frameState) {
         var commandStart = frameState.commandList.length;
 
@@ -453,6 +456,8 @@ define([
         // Update clipping planes
         var tilesetClippingPlanes = this._tileset.clippingPlanes;
         if (this._tile.clippingPlanesDirty && defined(tilesetClippingPlanes)) {
+            // Apply inverse transform relative to root tile transform to the model clipping plane
+            this._model._clippingPlaneModelMatrix = Matrix4.multiply(Matrix4.inverse(this._tile.computedTransform, scratchClippingPlaneMatrix), this._tileset._root.computedTransform, scratchClippingPlaneMatrix);
             // Dereference the clipping planes from the model if they are irrelevant.
             // Link/Dereference directly to avoid ownership checks.
             // This will also trigger synchronous shader regeneration to remove or add the clipping plane and color blending code.

Source/Scene/Instanced3DModel3DTileContent.js

@@ -462,6 +462,8 @@ define([
             // Update for clipping planes
             var tilesetClippingPlanes = this._tileset.clippingPlanes;
             if (this._tile.clippingPlanesDirty && defined(tilesetClippingPlanes)) {
+                // Apply root tile transforms to instanced model clipping planes
+                model._clippingPlaneModelMatrix = this._tileset._root.computedTransform;
                 // Dereference the clipping planes from the model if they are irrelevant - saves on shading
                 // Link/Dereference directly to avoid ownership checks.
                 model._clippingPlanes = (tilesetClippingPlanes.enabled && this._tile._isClipped) ? tilesetClippingPlanes : undefined;

Source/Scene/Model.js

@@ -537,6 +537,9 @@ define([
         this.clippingPlanes = options.clippingPlanes;
         // Used for checking if shaders need to be regenerated due to clipping plane changes.
         this._clippingPlanesState = 0;
+        // Tiles all reference the same clippingPlaneCollection, this additional transform is
+        // applied to account for additional child transforms.
+        this._clippingPlaneModelMatrix = Matrix4.IDENTITY;
 
         /**
          * This property is for debugging only; it is not for production use nor is it optimized.
@@ -4464,7 +4467,8 @@ define([
             var clippingPlanes = this._clippingPlanes;
             var currentClippingPlanesState = 0;
             if (defined(clippingPlanes) && clippingPlanes.enabled) {
-                Matrix4.multiply(context.uniformState.view3D, modelMatrix, this._modelViewMatrix);
+                var clippingPlanesModelMatrix = Matrix4.multiply(modelMatrix, this._clippingPlaneModelMatrix, this._modelViewMatrix);
+                Matrix4.multiply(context.uniformState.view3D, clippingPlanesModelMatrix, this._modelViewMatrix);
                 currentClippingPlanesState = clippingPlanes.clippingPlanesState;
             }