Bad visualization with small geometry

[mramato]

This might be multiple bugs, or it could be one issue manifesting in multiple places.

The below code snippet as reported on the forum is not giving the intended visualization. I actually think this code is bad to begin with because the width is way to big for the proximity of the data, something like 0.1 is more realistic, but changing it produces no visualization at all.

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

var segments = [
[-111.819822,33.264247,347.0125903148645,-111.819827,33.264247,347.0125903148645,-111.819828,33.264246,347.0125903148645,-111.819826,33.264248,347.0125903148645,-111.81981,33.264258,346.9642320459691]
];

for ( var iSeg = 0; iSeg < segments.length; iSeg++ ) {
    var positions = segments[ iSeg ];

    var corridor = new Cesium.GeometryInstance( {
        geometry : new Cesium.CorridorGeometry( {
            positions : Cesium.Cartesian3.fromDegreesArrayHeights( positions ),
            width : 10
        } ),
        attributes : {
            color : new Cesium.ColorGeometryInstanceAttribute.fromColor( Cesium.Color.RED )
        }
    } );

    viewer.scene.groundPrimitives.add( new Cesium.GroundPrimitive( {
        geometryInstance : corridor
    } ) );

}

viewer.camera.flyTo( {
    destination: Cesium.Cartesian3.fromDegrees( -111.820455, 33.264529, 750 )
} );

In order to get a better idea of the data, I used the below snippet. As you'll see the points do not line up with the polyline (the polyline is wrong). If you make the polyline a corridor with width: 0.1, it has a similar issue.

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

var positions = Cesium.Cartesian3.fromDegreesArray(
 [-111.819822,33.264247,
 -111.819827,33.264247,
 -111.819828,33.264246,
 -111.819826,33.264248,
 -111.81981,33.264258]);

viewer.entities.add({
    polyline : {
        positions : positions,
        material : Cesium.Color.RED
    }
});

positions.forEach(function(pos) {
    viewer.entities.add({
        position: pos,
        point : {
            pixelSize : 10
        }
    });
});

viewer.zoomTo(viewer.entities);

So there's definitely something wrong going on, but I have no idea what it is at this point.

[slozier]

PolylineGeometry.createGeometry calls PolylinePipeline.removeDuplicates which decided which points are duplicates by calling Cartesian3.equalsEpsilon on consecutive points with an epsilon of 1e-7 which return true if each coordinates are equal using CesiumMath.equalsEpsilon and the same epsilon.

In my opinion Cartesian3.equalsEpsilon isn't a very good test for deciding if points are duplicates since its results can be greatly affected by the coordinates.

For example:

a = Cesium.Cartesian3.fromDegreesArray([0,0,0.00000000001,0]);
Cesium.Cartesian3.equalsEpsilon(a[0],a[1], 1e-7); // = false
Cesium.Cartesian3.distance(a[0],a[1]); // = 0.00000111319...

b = Cesium.Cartesian3.fromDegreesArray([45,0,45.000001,0]);
Cesium.Cartesian3.equalsEpsilon(b[0],b[1], 1e-7); // = true
Cesium.Cartesian3.distance(b[0],b[1]); // = 0.111319...

If you try your second example with the following positions, then it works.

var positions = Cesium.Cartesian3.fromDegreesArray(
 [-1.819822,33.264247,
 -1.819827,33.264247,
 -1.819828,33.264246,
 -1.819826,33.264248,
 -1.81981,33.264258]);

[denverpierce]

Possibly related to this?

https://groups.google.com/forum/#!searchin/cesium-dev/Disabling$20vertex$20compression$20on$20a$20datasource/cesium-dev/pwl1UbCynwo/vq-3sA9oAgAJ

There's some more sample data in the forum post.

[hpinkos]

This is fixed

[cesium-concierge]

Congratulations on closing the issue! I found these Cesium forum links in the comments above:

https://groups.google.com/d/msg/cesium-dev/hoObR5ChpHQ/K3rrDe8lAQAJ
https://groups.google.com/forum/#!searchin/cesium-dev/Disabling$20vertex$20compression$20on$20a$20datasource/cesium-dev/pwl1UbCynwo/vq-3sA9oAgAJ

If this issue affects any of these threads, please post a comment like the following:

The issue at #3035 has just been closed and may resolve your issue. Look for the change in the next stable release of Cesium or get it now in the master branch on GitHub https://github.com/AnalyticalGraphicsInc/cesium.

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