rayTraceTest.js

rayTraceTest.js

var cesiumViewer = window.viewer.state ? window.viewer.state.viewer: window.viewer
var camera = cesiumViewer.scene.camera
var scene = cesiumViewer.scene

//var scratchCart3 = new Cesium.Cartesian3()

var radius = 5

cesiumViewer.entities.add(
{
    //id: "centerPixelBoundingSphere_"+Math.random(),
    position: camera.position,
    ellipsoid: {
        radii: new Cesium.Cartesian3(radius, radius, radius),
        fill: true,
        outline: true,
        outlineColor: Cesium.Color.RED.withAlpha( 0.5 ),
        material: Cesium.Color.RED.withAlpha(0.5)
    }
} )


var point1 = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 20, 20, 20), new Cesium.Cartesian3() )
var point1a = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 10, 10, 10), new Cesium.Cartesian3() )
var vPoint1 = Cesium.Cartesian3.subtract( point1a, point1, new Cesium.Cartesian3() )

cesiumViewer.entities.add({
    polyline: {
        positions : [point1, point1a],
        width : 2,
        color: Cesium.Color.BLUE,
        material: Cesium.Color.BLUE.withAlpha(0.5)
    }
});

scene.requestRender()

var point2 = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 20, 20, 20), new Cesium.Cartesian3() )
var point2a = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 15, 1, 15), new Cesium.Cartesian3() )
var vPoint2 = Cesium.Cartesian3.subtract( point2a, point2, new Cesium.Cartesian3() )

cesiumViewer.entities.add({
    polyline: {
        positions : [point2, point2a],
        width : 2,
        color: Cesium.Color.GREEN,
        material: Cesium.Color.GREEN.withAlpha(0.5)
    }
});

var point3 = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 20, 20, 20), new Cesium.Cartesian3() )
var point3a = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 20, 12, 12), new Cesium.Cartesian3() )
var vPoint3 = Cesium.Cartesian3.subtract( point3a, point3, new Cesium.Cartesian3() )

cesiumViewer.entities.add({
    polyline: {
        positions : [point3, point3a],
        width : 2,
        color: Cesium.Color.YELLOW,
        material: Cesium.Color.YELLOW.withAlpha(0.5)
    }
});

var point4 = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 20, 20, 20), new Cesium.Cartesian3() )
var point4a = Cesium.Cartesian3.subtract( camera.position, new Cesium.Cartesian3( 11, 9, 11), new Cesium.Cartesian3() )
var vPoint4 = Cesium.Cartesian3.subtract( point4a, point4, new Cesium.Cartesian3() )

cesiumViewer.entities.add({
    polyline: {
        positions : [point4, point4a],
        width : 2,
        color: Cesium.Color.RED,
        material: Cesium.Color.RED.withAlpha(0.5)
    }
});

scene.requestRender()

console.log( "blue line: is intersect: ",isIntersect(camera.position, 10, point1, vPoint1) )
console.log( "green line: is intersect: ",isIntersect(camera.position, 10, point2, vPoint2) )
console.log( "yellow line: is intersect: ",isIntersect(camera.position, 10, point3, vPoint3) )
console.log( "red line: is intersect: ",isIntersect(camera.position, 10, point4, vPoint4) )



function isIntersect( centerPosition, radius, pointPosition, pointDirection ) {

    var vCenter2Point = Cesium.Cartesian3.subtract( pointPosition, centerPosition, new Cesium.Cartesian3() )
    var mCenter2Point = Cesium.Cartesian3.magnitude( vCenter2Point )

    if( mCenter2Point < radius ) {
        return true
    }
    else {
        dotProduct = Cesium.Cartesian3.dot( vCenter2Point, pointDirection )
        if( dotProduct <= 0 ) {
            var vCenter2PointProjected = Cesium.Cartesian3.projectVector( vCenter2Point, pointDirection, new Cesium.Cartesian3() )

            var v = Cesium.Cartesian3.subtract( vCenter2Point, vCenter2PointProjected, new Cesium.Cartesian3() )
            if( Cesium.Cartesian3.magnitude( v ) <= radius ) {
                return true
            }
            else {
                return false
            }
        }
        else {
            return false
        }
    }

    //input
//     vector A
//     vector d
//     vector C
//     float r
//     //end of input

//     vector collisionPoint
//     vector v
//     vector CA = A-C
//     float rSquared = r*r
//     float vSquared
//     if(dotProduct(CA,CA) <= rSquared){
//         collisionPoint = A
//     }
//     else if(dotProduct(CA,d) <= 0){
//         v = CA - projection(CA,d)
//         vSquared = dotProduct(v,v)
//         if(vSquared <= rSquared){
//             collisionPoint = C + v - multiply(normalize(d),squareRoot(rSquared-vSquared))
//         }
//         else{
//             collisionPoint = none
//         }
//     }
//     else{
//         collisionPoint = none
//     }
}

red and blue lines intersects red sphere
yellow and green lines do not