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| var viewer = new Cesium.Viewer('cesiumContainer');
var CC3=Cesium.Cartesian3;
var camera = viewer.scene.camera;
var ellipsoid = viewer.scene.globe.ellipsoid;
var rad = 6371000; //Earth average radius
var entityN = viewer.entities.add({
label : {
show : false
}
});
var entityW = viewer.entities.add({
label : {
show : false
}
});
var entityS = viewer.entities.add({
label : {
show : false
}
});
var entityE = viewer.entities.add({
label : {
show : false
}
});
Sandcastle.addToolbarButton('horizon points', function() {
//h 大专栏 cesiumjsorizon basics
var dist=CC3.magnitude(camera.position);
var angle=Math.asin(rad/dist);
var toSurf=Math.sqrt(Math.pow(dist,2)-Math.pow(rad,2));
//'horizon arm'
var rotatee = camera.position.clone();
rotatee = CC3.negate(rotatee,new CC3());
CC3.normalize(rotatee,rotatee);
var rotater = new CC3(0,0,1);
CC3.cross(rotatee,rotater,rotater);
var rotated = new CC3();var cartesian = new CC3();
rotated = rotate(rotatee,rotater,angle);
cartesian = scaleVector(toSurf,rotated);
CC3.add(cartesian,camera.position,cartesian);
//north
dropOne(entityN,cartesian);
//east
cartesian = rotate(cartesian,rotatee,Math.PI/2); //rotatee now rotater
dropOne(entityE,cartesian);
//south
cartesian = rotate(cartesian,rotatee,Math.PI/2); //rotatee now rotater
dropOne(entityS,cartesian);
//west
cartesian = rotate(cartesian,rotatee,Math.PI/2); //rotatee now rotater
dropOne(entityW,cartesian);
});
function dropOne(entity,cartesian)
{
if (cartesian) {
var cartographic = ellipsoid.cartesianToCartographic(cartesian);
var longitudeString = Cesium.Math.toDegrees(cartographic.longitude).toFixed(2);
var latitudeString = Cesium.Math.toDegrees(cartographic.latitude).toFixed(2);
entity.position = cartesian;
entity.label.show = true;
entity.label.text = '(' + longitudeString + ', ' + latitudeString + ')';
} else {
entity.label.show = false;
}
}
function rotate(rotatee,rotater,angle)
{
//rotater: unit vector, angle:radians
//CCW looking from vector tip to vector base
var CC3=Cesium.Cartesian3;var rotated=new CC3();
var c = Math.cos(angle);var s = Math.sin(angle);
var dotScale = CC3.dot(rotatee,rotater,new CC3());
var rotaterScaled = scaleVector(dotScale,rotater);
var vPerpAxis = CC3.subtract(rotatee,rotaterScaled,new CC3()); //using Pythagoras theorem
var comp1 = scaleVector(c,vPerpAxis);
var vPerpPerpAxis = CC3.cross(rotater,vPerpAxis,new CC3()); //perp to both of these
var comp2 = scaleVector(s,vPerpPerpAxis);
return addVectors([rotaterScaled,comp1,comp2]);
}
function scaleVector(scale,vector)
{
var temp = new Cesium.Cartesian3();
temp.x=scale*vector.x;temp.y=scale*vector.y;temp.z=scale*vector.z;
return temp;
}
function addVectors(vectors)
{
var resultant=new Cesium.Cartesian3(0,0,0);
var i=0;while(i<vectors.length)
{
resultant.x+=vectors[i].x;
resultant.y+=vectors[i].y;
resultant.z+=vectors[i].z;
i+=1;
}
return resultant;
}
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