Cesium GroundPrimitive and Polygon on Terrain Rendering

[jamiesampey]

KML Graphics Roadmap: CesiumGS/cesium#2179

Vector Data on Terrain: CesiumGS/cesium#2172
Request for issue 2172: https://groups.google.com/forum/#!searchin/cesium-dev/polyline$20on$20terrain/cesium-dev/xqUZ-JUIxjU/sXfjXBxsa4EJ

Polygon on Terrain: CesiumGS/cesium#2618

[jamiesampey]

Cesium 1.13 included polygon on terrain rendering. release notes: http://cesiumjs.org/2015/09/01/Cesium-version-1.13-released/

The main class is GroundPrimitive which takes a GeometryInstance. Only one GroundPrimitive-wrapped GeometryInstance can be added at a time. Batching is not supported "at this time."

http://cesiumjs.org/Cesium/Build/Documentation/GroundPrimitive.html?classFilter=ground

It's probably better to use this class and not worry about manually "floating" the polygon a meter above the surface. Plus, hopefully any future advancements will use this class.

[jamiesampey]

AvyEyesView.prototype.addAvalanche = function(avalanche) {
    var avalanchePolygon = new Cesium.GeometryInstance({
        id: avalanche.extId,
        geometry: new Cesium.PolygonGeometry({
            polygonHierarchy: {
                positions: Cesium.Cartesian3.fromDegreesArrayHeights(avalanche.coords)
            }
        }),
        attributes: {
            color: new Cesium.ColorGeometryInstanceAttribute(1.0, 0, 0, 0.4)
        },
        appearance: new Cesium.PerInstanceColorAppearance({
            translucent: false
        })
 });

 this.cesiumViewer.scene.primitives.add(new Cesium.GroundPrimitive({
      geometryInstance: avalanchePolygon
 }));

    return avalanchePolygon;
}

and 

 $.getJSON("/rest/avydetails/" + pick.id, function(data) {

get pretty close, but I need to send a target ENTITY into flyTo()

[jamiesampey]

10/19/2015 INVESTIGATION

Use KML? https://cesiumjs.org/2015/05/07/New-KML-Examples/

Three required pieces for avalanche display:

1. Can I fly to it? YES for KML and Entities, no for GroundPrimitive.
2. Can I pick it? YES for KML, Entities, and GroundPrimitive.
3. Can I drape it over terrain? Yes for GroundPrimitive, sort of for Entities, NO for KML.

Vector Data on Terrain: CesiumGS/cesium#2172

https://groups.google.com/forum/#!searchin/cesium-dev/kml$20ground$20terrain/cesium-dev/xz2xwKogybY/jt8h174rknwJ

https://groups.google.com/forum/#!searchin/cesium-dev/kml$20ground$20terrain/cesium-dev/ixhw1BrmvJM/PhVXCHFA8XcJ

[jamiesampey]

Intermediate idea until KML or entities drape over terrain (#2172):

Make a draping ground primitive for each avy. The groundprimitive will handle the picking.

Make a "companion" entity for a fly to. Remove the entity immediately after the fly to leaving only the pickable, draped GroundPrimitive.

[jamiesampey]

Doesn't seem like Ground primitive is supported in the Entity API yet: https://groups.google.com/forum/#!searchin/cesium-dev/groundprimitive$20with$20entity/cesium-dev/M_ZDcDlNL10/iZKWb7w3CAAJ

Weird rendering problems occur on some GPUs with the ground primitive.

https://groups.google.com/forum/#!searchin/cesium-dev/entities$20vs$20primitives/cesium-dev/yyAXePPdNqE/oN5frxtI74UJ
http://cesiumjs.org/2015/02/02/Visualizing-Spatial-Data/

https://groups.google.com/forum/#!topic/cesium-dev/g-8wkhZYoGc

[jamiesampey]

Created this forum topic on 11-2-2015: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/6qt-wb-SohY

which resulted in this bug submitted on 11-5-2015: CesiumGS/cesium#3171

[jamiesampey]

This seems to have gotten better. Probably not completely fixed, but no plans to do further work on this right now.