# Problem with PolylineVolumeGraphics

1. A concise explanation of the problem you’re experiencing.

The shape I’m providing “surrounds” the z-axis, but the extrusion is always being drawn “above” the reference positions.

2. A minimal code example. If you’ve found a bug, this helps us reproduce and repair it.

var viewer = new Cesium.Viewer(‘cesiumContainer’);

//Use STK World Terrain

viewer.terrainProvider = new Cesium.CesiumTerrainProvider({

``````url: 'https://assets.agi.com/stk-terrain/v1/tilesets/world/tiles',

requestVertexNormals: true
``````

});

//Set the random number seed for consistent results.

Cesium.Math.setRandomNumberSeed(3);

var start = Cesium.JulianDate.fromDate(new Date());

var stop = Cesium.JulianDate.addSeconds(start, 360, new Cesium.JulianDate());

function computeFlightPath(lon, lat, radius, outPos) {

``````var sampledPos = new Cesium.SampledPositionProperty();

var count = 0;

for (var i = 0; i <= 270; i += 15) {

var time = Cesium.JulianDate.addSeconds(start, i, new Cesium.JulianDate());

var position = Cesium.Cartesian3.fromDegrees(

Cesium.Math.nextRandomNumber() * 500 + 1750);

outPos[count++] = position;

}

return sampledPos;
``````

}

function computeFinalFlightPath(a, b, outPos) {

``````var sampledPos = new Cesium.SampledPositionProperty();

for (var i = 0; i < a.length; i++) {

var time = Cesium.JulianDate.addSeconds(start, i, new Cesium.JulianDate());

var position = Cesium.Cartesian3.fromElements(

((a[i].x + b[i].x) * 0.5),

((a[i].y + b[i].y) * 0.5),

((a[i].z + b[i].z) * 0.5));

outPos[i] = position;

}

return sampledPos;
``````

}

function createFlightGraphics(sampledPos, pos, color) {

``````for (var p = 0; p < pos.length; p++) {

position: pos[p],

point: {

pixelSize : 8,

color: Cesium.Color.TRANSPARENT,

outlineColor: color,

outlineWidth: 3

}

});

}

availability: new Cesium.TimeIntervalCollection([new Cesium.TimeInterval({

start: start,

stop: stop

})]),

// Use our computed positions

position: sampledPos,

// Automatically compute orientation based on position movement.

orientation : new Cesium.VelocityOrientationProperty(sampledPos),

path: {

resolution: 1,

material: new Cesium.PolylineGlowMaterialProperty({

glowPower : 0.1,

color : color

}),

width : 10

}

});
``````

}

//Compute the position

var uav1Pos = ;

var uav1SampledPos = computeFlightPath(-83.60986232757568,41.653258658953995, 0.03, uav1Pos);

var uav2Pos = ;

var uav2SampledPos = computeFlightPath(-83.60986232757570,41.653258658953998, 0.033, uav2Pos);

var uav3Pos = ;

var uav3SampledPos = computeFinalFlightPath(uav1Pos, uav2Pos, uav3Pos);

// Create graphics

//createFlightGraphics(uav1SampledPos, uav1Pos, Cesium.Color.YELLOW);

//createFlightGraphics(uav2SampledPos, uav2Pos, Cesium.Color.RED);

createFlightGraphics(uav3SampledPos, uav3Pos, Cesium.Color.CYAN);

``````polylineVolume: {

positions: uav3Pos,

shape: [

new Cesium.Cartesian2(-500.0, -200.0),

new Cesium.Cartesian2( 500.0, -200.0),

new Cesium.Cartesian2( 500.0, 200.0),

new Cesium.Cartesian2(-500.0, 200.0)

],

material: Cesium.Color.BLUE.withAlpha(0.5),

outline: true,

outlineColor: Cesium.Color.BLACK

}
``````

});

viewer.zoomTo(viewer.entities);

``

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

Investigating a solution to another question on cesium-dev.

4. The Cesium version you’re using, your operating system and browser.

I’m at the head of main using Chrome 64.0.3282.186 on Windows 10.

HI Scott,

It looks like the extruded shape is indeed always “above” those positions. This makes sense when you are drawing the volume with positions on the surface, but otherwise it doesn’t. I’ve opened a new issue #6350 to track.

Thanks,

Gabby