Added missing functions to ConstantSpline

CHANGES.md

@@ -12,7 +12,7 @@ Change Log
 * `BingMapsImageryProvider` is no longer the default base imagery layer.
 * `BingMapsGeocoderService` is no longer the default geocoder service.
 * Cesium no longer ships with a demo Bing Maps API key.
-* `ClippingPlaneCollection` now uses `ClippingPlane` objects instead of`Plane` objects. [#6498](https://github.com/AnalyticalGraphicsInc/cesium/pull/6498) 
+* `ClippingPlaneCollection` now uses `ClippingPlane` objects instead of`Plane` objects. [#6498](https://github.com/AnalyticalGraphicsInc/cesium/pull/6498)
 
 ##### Deprecated :hourglass_flowing_sand:
 * `Particle.size`, `ParticleSystem.rate`, `ParticleSystem.lifeTime`, `ParticleSystem.life`, `ParticleSystem.minimumLife`, and `ParticleSystem.maximumLife` have been renamed to `Particle.imageSize`, `ParticleSystem.emissionRate`, `ParticleSystem.lifetime`, `ParticleSystem.particleLife`, `ParticleSystem.minimumParticleLife`, and `ParticleSystem.maximumParticleLife`. Use of the `size`, `rate`, `lifeTime`, `life`, `minimumLife`, and `maximumLife` parameters is deprecated and will be removed in Cesium 1.46.
@@ -49,6 +49,7 @@ Change Log
 * Fixed a bug causing crashes when setting colors on un-pickable models. [$6442](https://github.com/AnalyticalGraphicsInc/cesium/issues/6442)
 * Fix flicker when adding, removing, or modifying entities. [#3945](https://github.com/AnalyticalGraphicsInc/cesium/issues/3945)
 * Fixed crash bug in PolylineCollection when a polyline was updated and removed at the same time. [#6455](https://github.com/AnalyticalGraphicsInc/cesium/pull/6455)
+* Fixed crash when animating a glTF model with a single keyframe. [#6422](https://github.com/AnalyticalGraphicsInc/cesium/pull/6422)
 * Fixed Imagery Layers Texture Filters Sandcastle example. [#6472](https://github.com/AnalyticalGraphicsInc/cesium/pull/6472).
 * Fixed a bug causing Cesium 3D Tilesets to not clip properly when tiles were unloaded and reloaded. [#6484](https://github.com/AnalyticalGraphicsInc/cesium/issues/6484)
 * Improved rendering of glTF models that don't contain normals with a temporary unlit shader workaround. [#6501](https://github.com/AnalyticalGraphicsInc/cesium/pull/6501)

Source/Scene/ModelAnimationCache.js

@@ -114,6 +114,12 @@ define([
     ConstantSpline.prototype.evaluate = function(time, result) {
         return this._value;
     };
+    ConstantSpline.prototype.wrapTime = function(time) {
+        return 0.0;
+    };
+    ConstantSpline.prototype.clampTime = function(time) {
+        return 0.0;
+    };
 
     ModelAnimationCache.getAnimationSpline = function(model, animationName, animation, samplerName, sampler, input, path, output) {
         var key = getAnimationSplineKey(model, animationName, samplerName);

Specs/Scene/ModelSpec.js

@@ -1606,6 +1606,34 @@ defineSuite([
         expect(animations.update()).toEqual(false);
     });
 
+    it('animates a single keyframe', function() {
+        return Resource.fetchJson(animBoxesUrl).then(function(gltf) {
+            gltf.accessors['animAccessor_0'].count = 1;
+            gltf.accessors['animAccessor_1'].count = 1;
+
+            return loadModelJson(gltf).then(function(m) {
+                m.show = true;
+                var node = m.getNode('inner_box');
+                var time = JulianDate.fromDate(new Date('January 1, 2014 12:00:00 UTC'));
+                var animations = m.activeAnimations;
+                animations.add({
+                    name : 'animation_0',
+                    startTime : time
+                });
+
+                expect(node.matrix).toEqual(Matrix4.IDENTITY);
+                var previousMatrix = Matrix4.clone(node.matrix);
+
+                for (var i = 1; i < 4; ++i) {
+                    var t = JulianDate.addSeconds(time, i, new JulianDate());
+                    scene.renderForSpecs(t);
+                    expect(node.matrix).toEqual(previousMatrix);
+                }
+                primitives.remove(m);
+            });
+        });
+    });
+
     ///////////////////////////////////////////////////////////////////////////
 
     it('renders riggedFigure without animation', function() {