Rectangle issue

[mramato]

The below code (from KmlDataSource.js) fails because both west and east ends up being -Math.PI It works without convertLongitudeRange, but I'm using it in this case because I'm reading the data externally and values may extend beyond 180 degrees. Am I doing something wrong or is there a bug in convertLongitudeRange when values are +-PI?

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

var west = Cesium.Math.convertLongitudeRange(Cesium.Math.toRadians(-180));
var south = Cesium.Math.negativePiToPi(Cesium.Math.toRadians(-60));
var east = Cesium.Math.convertLongitudeRange(Cesium.Math.toRadians(180));
var north = Cesium.Math.negativePiToPi(Cesium.Math.toRadians(60));

viewer.entities.add({
    rectangle : {
        coordinates : new Cesium.Rectangle(west, south, east, north)
    }
});

It's possible that I need to special case something during KML load, but I'm just trying to confirm convertLongitudeRange behavior is correct.

[WarpDrive]

UPDATE: wait a minute, +180 is the same angle as -180. I'll check other values and see what happens.

I threw that function into a sandcastle app to play with it. This may not be a factor here, but the floor of -0.5 is -1, though one could easily think that it would be 0. Maybe it should be absolute value then floored?

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

var angle = 180/180*Math.PI;
var twoPi = 2*Math.PI;

var simplified = angle - Math.floor(angle / twoPi) * twoPi;
console.log(Math.floor(angle / twoPi));
console.log(simplified);

if (simplified < -Math.PI) {
   console.log(simplified + twoPi);
}
else if (simplified >= Math.PI) {
    console.log(simplified - twoPi);
}
else {console.log(simplified);};

If you change >= to > then -180 is wrong instead of 180 being wrong. When I get time I could figure out a fix, unless someone beats me to it.

[WarpDrive]

Re-reading what you've wrote, I see what you mean, why does this work and not with the convert function. I should read more carefully!

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

var west = -Math.PI;
var south = -60/180*Math.PI;
var east = Math.PI
var north = 60/180*Math.PI;

viewer.entities.add({
    rectangle : {
        coordinates : new Cesium.Rectangle(west, south, east, north)
    }
});

It fails if east and west signs are the same, or if east is negative and west is positive, but works if west is negative and east positive.

[WarpDrive]

Here's a re-write of convertLongitudeRange that retains the sign of Math.PI inputs.

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

var angle = 180/180*Math.PI;
var twoPi = 2*Math.PI;

//extract sign
var sign=1;if(angle<0){sign=-1;}
angle=Math.abs(angle);

//remove extra revolutions
var simplified = angle - Math.floor(angle / twoPi) * twoPi;

//convert to other hemi-circle
if(simplified>Math.PI)
{
    simplified=Math.PI-(simplified-Math.PI);
    sign*=-1;
}

//re-apply sign
simplified*=sign;

//return the value
console.log(simplified/Math.PI*180);

[bagnell]

Why not use Cesium.Math.negativePiToPi for both east and west? Even though it's the same angle it will preserve the sign.

[mramato]

Why not use Cesium.Math.negativePiToPi for both east and west? Even though it's the same angle it will preserve the sign.

Most likely because I have no idea what I'm doing and convertLongitudeRange just sounded like the right function :) So what is the use case for convertLongitudeRange?

[WarpDrive]

Ya, that function works well, I'm not sure why one would use convertLongitudeRange rather than negativePiToP now that Bagnell mentioned it. Both functions go back to 2012 though.

var viewer = new Cesium.Viewer('cesiumContainer');
console.log(Cesium.Math.negativePiToPi(-Math.PI));
console.log(Cesium.Math.negativePiToPi(Math.PI));
console.log(Cesium.Math.negativePiToPi(-Math.PI-0.1));
console.log(Cesium.Math.negativePiToPi(Math.PI+0.1));

I noticed that ced9b31 also uses negativePitoPi though latitude only spans -Pi/2 to +Pi/2 , but I doubt anyone would plug in a latitude value outside of that range.

[bagnell]

@mramato I don't know. I looked at the history and it was added when Cesium was first submitted to GitHub. It's not used anywhere though.