WallGeometry handling positions incorrectly

[hpinkos]

Reported by @primozs

WallGeometry is not iterating through these positions correctly, resulting in trying to normalize the zero vector:

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

var dataFail = [{"x":4275839.559924875,"y":1108128.491490115,"z":4587218.256350457},{"x":4275839.560187584,"y":1108128.4915581993,"z":4587218.255867044},{"x":4275839.560187584,"y":1108128.4915581993,"z":4587218.255867044},{"x":4275839.560187584,"y":1108128.4915581993,"z":4587218.255867044},{"x":4275839.560187584,"y":1108128.4915581993,"z":4587218.255867044},{"x":4275839.560187584,"y":1108128.4915581993,"z":4587218.255867044},{"x":4275839.559983776,"y":1108128.4926396976,"z":4587218.25594444}];

var wall = {
  wall: {
    positions: dataFail, 
    material: Cesium.Color.fromCssColorString('red').withAlpha(0.2),
    outline: true,
    outlineColor: Cesium.Color.fromCssColorString('red').withAlpha(0.2)
  }
};
 
viewer.entities.add(wall);

viewer.scene.camera.flyTo({
    destination: new Cesium.Cartesian3(4275945.9824068565, 1107800.9025642173, 4587695.880722421),
});

[easternmotors]

Can confirm this is still an issue in 1.67

[tkazik]

Yes, this bug is still valid...also in 1.69 (just took us 1h to figure that out :/).
The issue seems to be the following: If you add Cartesian3 with the same values, the difference will be the zero vector and normalization/division with a zero vector will make the program crash.
We did the following workaround: Only add points to the wall (tmpPos), that have a difference bigger than an epsilon3:

            var tmpC3 = new Cartesian3(W_t_W_C.x, W_t_W_C.y, W_t_W_C.z);
            var myDiff = new Cartesian3(0,0,0);
            if (tmpPos.length > 0 ) {
                Cartesian3.subtract(tmpC3, tmpPos[tmpPos.length-1], myDiff);
                if (!Cartesian3.equalsEpsilon(myDiff, Cartesian3.ZERO, CesiumMath.EPSILON3)) {
                    tmpPos.push(tmpC3)
                } else {
                    console.log("diff is ZEROOOO");
                }
            } else {
                tmpPos.push(tmpC3)
            }

But yes, it would be nicer, if that bug would be fixed within Cesium :) Thx!