Fix ellipse triangulation

[hpinkos]

Fixes #3078

This also fixes a crash if you tried to create an ellipse with VertexFormat.ALL. The tangents and binormals weren't normalized.

Before:

After:

[hpinkos]

normals/tangents/binormals and texture coordiantes should be correct:

[bagnell]

Try this example code that doesn't generate that many triangles:

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

scene.primitives.add(new Cesium.Primitive({
    geometryInstances : new Cesium.GeometryInstance({
        geometry : Cesium.GeometryPipeline.toWireframe(Cesium.EllipseGeometry.createGeometry(new Cesium.EllipseGeometry({
            center : Cesium.Cartesian3.fromDegrees(-100.0, 40.0),
            semiMinorAxis : 300000.0,
            semiMajorAxis : 400000.0,
            vertexFormat : Cesium.PerInstanceColorAppearance.VERTEX_FORMAT,
            granularity : Cesium.Math.PI / 32
        }))),
        attributes: {
            color: Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.RED)
        }
    }),
    appearance : new Cesium.PerInstanceColorAppearance({
        translucent : false,
        closed : true
    }),
    asynchronous : false
}));

It looks like there are 22 triangles and 16 vertices. If you put a breakpoint in EllipseGeometry.createGeometry, there are 24 triangles and 18 vertices in the mesh.

[hpinkos]

@bagnell that's because there are duplicate positions at the points on the left and right end. It was that way before I changed the code. I'll see if I can fix it though.

[hpinkos]

@bagnell ready

[pjcozzi]

@bagnell any update here?

[bagnell]

Looks good. Thanks @hpinkos!