Merge pull request #8499 from AnalyticalGraphicsInc/negativePickFix

Made GlobeSurfaceTile.pick not pick triangles behind the ray
CesiumGS · Dec 30, 2019 · 2bc678a · 2bc678a
2 parents 6b42340 + 5082e42
commit 2bc678a
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Showing 4 changed files with 34 additions and 10 deletions.
diff --git a/CHANGES.md b/CHANGES.md
@@ -1,7 +1,7 @@
 Change Log
 ==========
 
-### 1.65.0 - 2020-01-02
+### 1.65.0 - 2020-01-06
 
 ##### Fixes :wrench:
 * Fixed Geocoder auto-complete suggestions when hosted inside Web Components. [#8425](https://github.com/AnalyticalGraphicsInc/cesium/pull/8425)

diff --git a/Source/Core/IntersectionTests.js b/Source/Core/IntersectionTests.js
@@ -67,7 +67,7 @@ import Ray from './Ray.js';
     var scratchQVec = new Cartesian3();
 
     /**
-     * Computes the intersection of a ray and a triangle as a parametric distance along the input ray.
+     * Computes the intersection of a ray and a triangle as a parametric distance along the input ray. The result is negative when the triangle is behind the ray.
      *
      * Implements {@link https://cadxfem.org/inf/Fast%20MinimumStorage%20RayTriangle%20Intersection.pdf|
      * Fast Minimum Storage Ray/Triangle Intersection} by Tomas Moller and Ben Trumbore.

diff --git a/Source/Scene/GlobeSurfaceTile.js b/Source/Scene/GlobeSurfaceTile.js
@@ -164,12 +164,12 @@ import TerrainState from './TerrainState.js';
             var v2 = getPosition(encoding, mode, projection, vertices, i2, scratchV2);
 
             var t = IntersectionTests.rayTriangleParametric(ray, v0, v1, v2, cullBackFaces);
-            if (defined(t) && t < minT) {
+            if (defined(t) && t < minT && t >= 0.0) {
                 minT = t;
             }
         }
 
-        return minT < Number.MAX_VALUE ? Ray.getPoint(ray, minT, result) : undefined;
+        return minT !== Number.MAX_VALUE ? Ray.getPoint(ray, minT, result) : undefined;
     };
 
     GlobeSurfaceTile.prototype.freeResources = function() {

diff --git a/Specs/Scene/GlobeSurfaceTileSpec.js b/Specs/Scene/GlobeSurfaceTileSpec.js
@@ -311,8 +311,9 @@ describe('Scene/GlobeSurfaceTile', function() {
         });
 
         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.
+            // Pick root tile (level=0, x=0, y=0) from the east side towards the west.
+            // Based on heightmap triangle processing order the west triangle will be tested first, followed
+            // by the east triangle. But since the east triangle is closer we expect it to be the pick result.
             var terrainProvider = new EllipsoidTerrainProvider();
 
             var tile = new QuadtreeTile({
@@ -326,10 +327,33 @@ describe('Scene/GlobeSurfaceTile', function() {
             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 origin = new Cartesian3(50000000.0, -1.0, 0.0);
+                var direction = new Cartesian3(-1.0, 0.0, 0.0);
+                var ray = new Ray(origin, direction);
+                var cullBackFaces = false;
+                var pickResult = tile.data.pick(ray, undefined, undefined, cullBackFaces);
+                expect(pickResult.x).toBeGreaterThan(0.0);
+            });
+        });
+
+        it('ignores triangles that are behind the ray', function() {
+            // Pick root tile (level=0, x=0, y=0) from the center towards the east side (+X).
+            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 origin = new Cartesian3(0.0, -1.0, 0.0);
+                var direction = new Cartesian3(1.0, 0.0, 0.0);
+                var ray = new Ray(origin, direction);
                 var cullBackFaces = false;
                 var pickResult = tile.data.pick(ray, undefined, undefined, cullBackFaces);
                 expect(pickResult.x).toBeGreaterThan(0.0);