Merge pull request #8390 from AnalyticalGraphicsInc/tilePickFix

Fixed tile triangle picking

Author: lilleyse

CHANGES.md

@@ -8,6 +8,7 @@ Change Log
 * Fixed terrain tile culling problems when under ellipsoid. [#8397](https://github.com/AnalyticalGraphicsInc/cesium/pull/8397)
 * Fixed primitive culling when below the ellipsoid but above terrain. [#8398](https://github.com/AnalyticalGraphicsInc/cesium/pull/8398)
 * Improved the translucency calculation for the Water material type. [#8455](https://github.com/AnalyticalGraphicsInc/cesium/pull/8455)
+* Fixed globe picking so that it returns the closest intersecting triangle instead of the first intersecting triangle. [#8390](https://github.com/AnalyticalGraphicsInc/cesium/pull/8390)
 
 ##### Additions :tada:
 * Added `Globe.backFaceCulling` to support viewing terrain from below the surface. [#8470](https://github.com/AnalyticalGraphicsInc/cesium/pull/8470)

Source/Scene/GlobeSurfaceTile.js

@@ -7,6 +7,7 @@ import IndexDatatype from '../Core/IndexDatatype.js';
 import IntersectionTests from '../Core/IntersectionTests.js';
 import OrientedBoundingBox from '../Core/OrientedBoundingBox.js';
 import PixelFormat from '../Core/PixelFormat.js';
+import Ray from '../Core/Ray.js';
 import Request from '../Core/Request.js';
 import RequestState from '../Core/RequestState.js';
 import RequestType from '../Core/RequestType.js';
@@ -139,7 +140,6 @@ import TerrainState from './TerrainState.js';
     var scratchV0 = new Cartesian3();
     var scratchV1 = new Cartesian3();
     var scratchV2 = new Cartesian3();
-    var scratchResult = new Cartesian3();
 
     GlobeSurfaceTile.prototype.pick = function(ray, mode, projection, cullBackFaces, result) {
         var mesh = this.renderedMesh;
@@ -150,9 +150,11 @@ import TerrainState from './TerrainState.js';
         var vertices = mesh.vertices;
         var indices = mesh.indices;
         var encoding = mesh.encoding;
+        var indicesLength = indices.length;
 
-        var length = indices.length;
-        for (var i = 0; i < length; i += 3) {
+        var minT = Number.MAX_VALUE;
+
+        for (var i = 0; i < indicesLength; i += 3) {
             var i0 = indices[i];
             var i1 = indices[i + 1];
             var i2 = indices[i + 2];
@@ -161,13 +163,13 @@ import TerrainState from './TerrainState.js';
             var v1 = getPosition(encoding, mode, projection, vertices, i1, scratchV1);
             var v2 = getPosition(encoding, mode, projection, vertices, i2, scratchV2);
 
-            var intersection = IntersectionTests.rayTriangle(ray, v0, v1, v2, cullBackFaces, scratchResult);
-            if (defined(intersection)) {
-                return Cartesian3.clone(intersection, result);
+            var t = IntersectionTests.rayTriangleParametric(ray, v0, v1, v2, cullBackFaces);
+            if (defined(t) && t < minT) {
+                minT = t;
             }
         }
 
-        return undefined;
+        return minT < Number.MAX_VALUE ? Ray.getPoint(ray, minT, result) : undefined;
     };
 
     GlobeSurfaceTile.prototype.freeResources = function() {

Specs/Scene/GlobeSurfaceTileSpec.js

@@ -5,6 +5,7 @@ import { Cartesian3 } from '../../Source/Cesium.js';
 import { Cartesian4 } from '../../Source/Cesium.js';
 import { createWorldTerrain } from '../../Source/Cesium.js';
 import { Ellipsoid } from '../../Source/Cesium.js';
+import { EllipsoidTerrainProvider } from '../../Source/Cesium.js';
 import { GeographicTilingScheme } from '../../Source/Cesium.js';
 import { Ray } from '../../Source/Cesium.js';
 import { GlobeSurfaceTile } from '../../Source/Cesium.js';
@@ -308,6 +309,32 @@ describe('Scene/GlobeSurfaceTile', function() {
                 expect(cartographic.height).toBeGreaterThan(-500.0);
             });
         });
+
+        it('gets correct result when a closer triangle is processed after a farther triangle', function() {
+            // Pick root tile (0,0). It will intersect a triangle on the east and the west side.
+            // The east triangle is closer and should be the pick result even though the west triangle is checked first.
+            var terrainProvider = new EllipsoidTerrainProvider();
+
+            var tile = new QuadtreeTile({
+                tilingScheme : new GeographicTilingScheme(),
+                level : 0,
+                x : 0,
+                y : 0
+            });
+
+            processor.frameState = scene.frameState;
+            processor.terrainProvider = terrainProvider;
+
+            return processor.process([tile]).then(function() {
+                var ray = new Ray(
+                    new Cartesian3(50000000.0, 0.0, 0.0),
+                    // nudge the direction to be pointing at the (0,0) tile
+                    new Cartesian3(-0.9999422718925407, -0.007344489332226594, -0.007842917749982258));
+                var cullBackFaces = false;
+                var pickResult = tile.data.pick(ray, undefined, undefined, cullBackFaces);
+                expect(pickResult.x).toBeGreaterThan(0.0);
+            });
+        });
     }, 'WebGL');
 
     describe('eligibleForUnloading', function() {