Hole in animated ellipsoid entity

[hpinkos]

An ellipsoid using a SampledProperty doesn't render correctly at the north pole.
Reported in the forum: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/4ylMB9ou7YA

This example uses a SampledProperty for the radius, but the issue also occurs when using a SampledPositionProperty for the position.

var viewer = new Cesium.Viewer('cesiumContainer');
var start = Cesium.JulianDate.now();
var stop = Cesium.JulianDate.addDays(start, 1, new Cesium.JulianDate());

var startRadius = new Cesium.Cartesian3(100000, 100000, 100000);
var endRadius = new Cesium.Cartesian3(200000, 200000, 200000);
var radius = new Cesium.SampledProperty(Cesium.Cartesian3);
radius.addSample(start, startRadius);
radius.addSample(stop, endRadius);

viewer.entities.add({
    name: 'animated ellipsoid with hole',
    position: Cesium.Cartesian3.fromDegrees(-120, 35),
    ellipsoid: {
        radii: radius,
        outline: false,
        fill: true,
        material: Cesium.Color.RED
    }
});

viewer.entities.add({
    name: 'static ellipsoid with no hole',
    position: Cesium.Cartesian3.fromDegrees(-115, 35),
    ellipsoid: {
        radii: startRadius,
        outline: false,
        fill: true,
        material: Cesium.Color.RED
    }
});

viewer.zoomTo(viewer.entities);

[mramato]

This is a weird bug but I tracked it down primitive.modelMatrix. Basically, if you set GeometryInstance.modelMatrix and leave Primitive.modelMatrix alone, it shows up correctly. But if you don't set GeometryInstance.modelMatrix and instead set Primitive.modelMatrix, the problem occurs. The EllipsoidVisualizer does it this way to provide a fast path specifically for ellipsoid animation, the code is all perfectly valid at the Entity level and the bug is somewhere in Primitive.

Here's a sample that reproduces the problem. Change the last line to ellipsoidInstance.modelMatrix = modelMatrix; and the problem goes away.

// Create the viewer.
var viewer = new Cesium.Viewer('cesiumContainer');
var scene = viewer.scene;

// Draw a blue ellipsoid and position it on the globe surface.

var radii = new Cesium.Cartesian3(200000.0, 200000.0, 300000.0);
// Ellipsoid geometries are initially centered on the origin.
// We can use a model matrix to position the ellipsoid on the
// globe surface.
var positionOnEllipsoid = Cesium.Cartesian3.fromDegrees(-100.0, 40.0);
var modelMatrix = Cesium.Matrix4.multiplyByTranslation(
    Cesium.Transforms.eastNorthUpToFixedFrame(positionOnEllipsoid),
    new Cesium.Cartesian3(0.0, 0.0, radii.z), new Cesium.Matrix4()
);
// Create a ellipsoid geometry.
var ellipsoidGeometry = new Cesium.EllipsoidGeometry({
    vertexFormat : Cesium.PerInstanceColorAppearance.VERTEX_FORMAT,
    radii : radii
});
// Create a geometry instance using the geometry
// and model matrix created above.
var ellipsoidInstance = new Cesium.GeometryInstance({
    geometry : ellipsoidGeometry,
    attributes : {
        color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.BLUE)
    }
});
// Add the geometry instance to primitives.
var primitive = scene.primitives.add(new Cesium.Primitive({
    geometryInstances : ellipsoidInstance,
    appearance : new Cesium.PerInstanceColorAppearance({
        translucent : false,
        closed : true
    })
}));

primitive.modelMatrix = modelMatrix;

[hpinkos]

Also see CZML example posted by @kjartab in #3354

[hpinkos]

It looks like the first 60 or so positions are being set to (0, 0, 1) somehow
So some triangles have zero area
like triangle with indices [65, 1, 0]