How to create a sphere at the Sun's location?

[Daniel Oneil]

I'm trying to create a big gold sphere to represent the Sun but it's not working. I see the Earth but no other objects. Here's my code:

  <script>
    var viewer = new Cesium.Viewer('cesiumContainer');
    viewer.extend(Cesium.viewerEntityMixin);
   
    viewer.scene.camera.frustum.far = 1e11;  //Overwrite the distance to the far wall of the viewing frustum.
   
    var scene = viewer.scene ;
    var primitives = scene.primitives;

     radius = 1000;        
    var sphereGeometry = new Cesium.SphereGeometry({
        vertexFormat : Cesium.PerInstanceColorAppearance.VERTEX_FORMAT,
        radius : radius
});
    var instances = [];            // Array to hold geometry instances
   
var date = new Date('August 31, 2014 12:00:00 EST');
var julianDate = Cesium.JulianDate.fromDate(date, Cesium.TimeStandard.UTC);

var pointInSpace = new Cesium.Cartesian3(1.0,1.0,1.0);                   // Get the Sun's position.
Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame(julianDate, pointInSpace) ;

var sphereModelMatrix;
    sphereModelMatrix = Cesium.Matrix3.IDENTITY * pointInSpace ;
   
    instances.push(new Cesium.GeometryInstance({
        geometry : sphereGeometry,
        modelMatrix : sphereModelMatrix,
        attributes : {
            color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.GOLD)
        }
    }));
   
primitives.add(new Cesium.Primitive({
    geometryInstances : instances,
    appearance : new Cesium.PerInstanceColorAppearance({
        translucent : false,
        closed : true
    })
}));
  </script>

Corrections and recommendations would be appreciated.

[Patrick Cozzi]

Hi Daniel,

I'm not able to debug your code right now, but first try placing a label at the position you think the sun is at.  This way it will be big enough that you know you'll see it.  I suspect the 1,000 meters used now will be hard to spot.

Also, the Moon implementation may have some code of interest.

Patrick

[Ed Mackey]

Don't forget to ask Cesium to render stuff that far out.

    viewer.scene.camera.frustum.far = 1e12;

--Ed.

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[Daniel Oneil]

The next attempt to put a giant volume at the location of the Sun starts with the Sandcastle volumes example.
A Cesium Inspector was added and when I click on view frustum, it indicates two objects, i.e., Earth and Moon.
The far wall of the viewing frustum is set to 1e12. The viewer is set to track and select the entity but the camera shows the Earth.

Please let me know whether I'm using the Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame function correctly.

 <script>
var e;                                             // global variable for entity
function createPrimitives(scene) {
    var primitives = scene.primitives;

    var date = new Date('November 02, 2014 12:00:00 EST');

    var julianDate = Cesium.JulianDate.fromDate(date, Cesium.TimeStandard.UTC);

    var pointInSpace = new Cesium.Cartesian3(1.0,1.0,1.0);

    Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame(julianDate, pointInSpace) ;
   
   console.log(pointInSpace);
   e = primitives.add(new Cesium.EllipsoidPrimitive({
        center : pointInSpace,
        radii : new Cesium.Cartesian3(50000000.0, 50000000.0, 50000000.0),     // 50M meter radius
        material : Cesium.Material.fromType(Cesium.Material.RimLightingType)
    }));

}

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

    viewer.scene.camera.frustum.far = 1e12;            //Move the far wall of the viewing frustum.
    viewer.extend(Cesium.viewerCesiumInspectorMixin);  //Add Cesium Inspector
   
    var scene = viewer.scene ;
    scene.skyBox.show = false ;                        // Turn off the sky box
    scene.sun.show = false ;                           // Don't show the Sun
   
    viewer.trackedEntity = e;                         //Camera will now track the entity
    viewer.selectedEntity = e;                        //Selection will now appear over object

viewer.screenSpaceEventHandler.setInputAction(function(movement) {
    var pickedPrimitive = viewer.scene.pick(movement.endPosition);
 //   Sandcastle.highlight(pickedPrimitive);
}, Cesium.ScreenSpaceEventType.MOUSE_MOVE);

createPrimitives(viewer.scene);

 </script>

[Daniel Oneil]

I changed the call to the compute Sun position to:

    var pointInSpace = new Cesium.Cartesian3(1.0,1.0,1.0);

    pointInSpace = Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame(julianDate, pointInSpace) ;
 
It did not help.

On the Web Console there is an error message:
TypeError: n.NegativePiToPi is not a function                     Cesium.js:388

[Daniel Oneil]

I upgraded to Cesium-1.3 and I'm still getting the n.NegativePiToPi is not a function error at Cesium.js line 388.

[Ed Mackey]

Hi Dan,

Give this a try with the latest copy of Cesium.

            --Ed.

    <script>

        var solarRadiusInMeters = 6.955e8;

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

        viewer.scene.camera.frustum.far = 1e12;            //Move the far wall of the viewing frustum.
        viewer.extend(Cesium.viewerCesiumInspectorMixin);  //Add Cesium Inspector

        var scene = viewer.scene;
        scene.skyBox.show = false;                        // Turn off the sky box

        scene.sun.show = false;                           // Don't show the default Sun

        // Turn on sun lighting of the globe.
        scene.globe.enableLighting = true;

        // Create a Yellow rim-lit material.
        var material = Cesium.Material.fromType(Cesium.Material.RimLightingType);
        material.uniforms.color = Cesium.Color.YELLOW;

        // Create Sun graphics primitive.
        var sunEllipsoid = viewer.scene.primitives.add(new Cesium.EllipsoidPrimitive({
            center: new Cesium.Cartesian3(),  // For now, place the Sun at the origin.
            radii: new Cesium.Cartesian3(solarRadiusInMeters, solarRadiusInMeters, solarRadiusInMeters),
            material: material
        }));

        // Allocate "new" variables outside of the render loop when possible, to reduce garbage collection.
        var sunPosition = new Cesium.Cartesian3();
        var icrfToFixedScratch = new Cesium.Matrix3();

        // Update the camera and the Sun with each animation frame.
        function icrf(scene, time) {
            if (scene.mode !== Cesium.SceneMode.SCENE3D) {
                return;
            }

            var icrfToFixed = Cesium.Transforms.computeIcrfToFixedMatrix(time, icrfToFixedScratch);
            if (Cesium.defined(icrfToFixed)) {
                // Update the camera with the new ICRF rotation
                scene.camera.transform = Cesium.Matrix4.fromRotationTranslation(icrfToFixed);

                // Compute Sun position in Inertial.
                Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame(time, sunPosition);

                // Transform Sun position from Inertial to Fixed.
                Cesium.Matrix3.multiplyByVector(icrfToFixed, sunPosition, sunPosition);

                // Update the Sun's modelMatrix to move it from the origin to its new position for this animation frame.
                sunEllipsoid.modelMatrix = Cesium.Matrix4.fromRotationTranslation(Cesium.Matrix3.IDENTITY, sunPosition);
            }
        }
        scene.preRender.addEventListener(icrf);

    </script>

[Daniel Oneil]

Ed -

Thanks for the reply. I copied the Javascript into a local copy of Sandcastle running on Cesium 1.3 and received the following error:

An error occurred while rendering. Rendering has stopped.

DeveloperError: translation is required. DeveloperError@http://localhost:8080/Source/Core/DeveloperError.js:43:13 Matrix4.fromRotationTranslation@http://localhost:8080/Source/Core/Matrix4.js:302:13 icrf@http://localhost:8080/Apps/Sandcastle/templates/bucket.html:44:17 Event.prototype.raiseEvent@http://localhost:8080/Source/Core/Event.js:146:17 render@http://localhost:8080/Source/Scene/Scene.js:1353:9 Scene.prototype.render@http://localhost:8080/Source/Scene/Scene.js:1410:13 CesiumWidget.prototype.render@http://localhost:8080/Source/Widgets/CesiumWidget/CesiumWidget.js:600:13 render@http://localhost:8080/Source/Widgets/CesiumWidget/CesiumWidget.js:70:25

The entire viewing area of Sandcastle was yellow with a little black spot in the middle.

[Ed Mackey]

Odd, that would mean that "sunPosition" is undefined in the "icrf" function.  Of course I tested this (against master) and didn't see that problem here.  You could try wrapping that last statement inside an "if (Cesium.defined(sunPosition))" check, but I don't understand why such a check would be needed, since we already check the rotation matrix a few lines before.

I submitted a pull request, if anyone else wants to test it:

https://github.com/AnalyticalGraphicsInc/cesium/pull/2288

               --Ed.

[Hyper Sonic]

Over at

https://gist.github.com/emackey/53f4db126209bb590821

If you copy the code between //Sandcastle_Begin and //Sandcastle_End then paste it to

http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html

It works! The star-field doesn't show up though, just the Sun and Moon. I like the fact that it is astronomically correct, just like the Moon. You actually have to travel about 150 GigaMeters from the Earth to get to the Sun. By default you can only see 50 MegaMeters, but this code changes the far clip plane. Also the Sun is displayed with it's actual 1.4 GigaMeter diameter (contrast that with Earth's 0.012 GigaMeter diameter!) It could use a texture though, the Moon has one.

[Hyper Sonic]

change

sunEllipsoid.modelMatrix = Cesium.Matrix4.fromRotationTranslation(Cesium.Matrix3.IDENTITY, sunPosition, sunModelMatrixScratch);

to

sunEllipsoid.modelMatrix = Cesium.Matrix4.fromRotationTranslation(Cesium.Matrix3.IDENTITY, {x:1000000000,y:0,z:0}, sunModelMatrixScratch);

To really get a feel of how large the sun is! Instead of 150 GigaMeters away from the Earth the Sun is now a mere 1 GigaMeter away from Earth (center to center that is, since the Sun has about a 0.7 GigaMeter radius its about 300 MegaMeters away from the surface, which is why the Moon is sometimes inside the Sun as it has a 384 MegaMeter orbit.) Cesium can be a useful tool to study the Solar System!

[bhawna daryani]

I tried running it on 1.37 sandcastle and I get

An error occurred while rendering. Rendering has stopped.

undefined
TypeError: Cannot set property transform of #<Camera> which has only a getter
TypeError: Cannot set property transform of #<Camera> which has only a getter
at icrf (<anonymous>:34:32)
at Event.raiseEvent (https://cesiumjs.org/Cesium/Source/Core/Event.js:142:30)
at render (https://cesiumjs.org/Cesium/Source/Scene/Scene.js:2623:26)
at Scene.render (https://cesiumjs.org/Cesium/Source/Scene/Scene.js:2702:13)
at CesiumWidget.render (https://cesiumjs.org/Cesium/Source/Widgets/CesiumWidget/CesiumWidget.js:686:25)
at render (https://cesiumjs.org/Cesium/Source/Widgets/CesiumWidget/CesiumWidget.js:71:32)

[Gabby Getz]

Hi Bhawna,

Can you provide the code snippet you ran?

Thanks,

Gabby

[bhawna daryani]

Hey Gabby,

I ran this on 1.37 sandcastle.

//Sandcastle_Begin
	var solarRadiusInMeters = 6.955e8;

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

	viewer.scene.camera.frustum.far = 1e12; //Move the far wall of the viewing frustum.
	var scene = viewer.scene;

	scene.skyBox.show = false; // Turn off the sky box
	scene.sun.show = false; // Don't show the default Sun
	// Turn on sun lighting of the globe.
	scene.globe.enableLighting = true;
	// Create a Yellow rim-lit material.
	var material = Cesium.Material.fromType(Cesium.Material.RimLightingType);
	material.uniforms.color = Cesium.Color.YELLOW;
	// Create Sun graphics primitive.

var sunEllipsoid = scene.primitives.add(new Cesium.EllipsoidPrimitive({

	center: new Cesium.Cartesian3(), // For now, place the Sun at the origin.
	radii: new Cesium.Cartesian3(solarRadiusInMeters, solarRadiusInMeters, solarRadiusInMeters),
	material: material
	}));
	// Allocate "new" variables outside of the render loop when possible, to reduce garbage collection.
	var sunPosition = new Cesium.Cartesian3();
	var icrfToFixedScratch = new Cesium.Matrix3();

var sunModelMatrixScratch = new Cesium.Matrix4();

	// Update the camera and the Sun with each animation frame.
	function icrf(scene, time) {
	if (scene.mode !== Cesium.SceneMode.SCENE3D) {
	return;
	}
	var icrfToFixed = Cesium.Transforms.computeIcrfToFixedMatrix(time, icrfToFixedScratch);
	if (Cesium.defined(icrfToFixed)) {
	// Update the camera with the new ICRF rotation
	scene.camera.transform = Cesium.Matrix4.fromRotationTranslation(icrfToFixed);
	// Compute Sun position in Inertial.
	Cesium.Simon1994PlanetaryPositions.computeSunPositionInEarthInertialFrame(time, sunPosition);
	// Transform Sun position from Inertial to Fixed.
	Cesium.Matrix3.multiplyByVector(icrfToFixed, sunPosition, sunPosition);
	// Update the Sun's modelMatrix to move it from the origin to its new position for this animation frame.

	sunEllipsoid.modelMatrix = Cesium.Matrix4.fromRotationTranslation(Cesium.Matrix3.IDENTITY, sunPosition, sunModelMatrixScratch);
	}
	}

	scene.preRender.addEventListener(icrf);
	//Sandcastle_End

[Gabby Getz]

The offending line is 

scene.camera.transform = Cesium.Matrix4.fromRotationTranslation(icrfToFixed);

You can't set the camera's transform directly. Take a look at the camera documentation for the methods you can use, particularly lookAtTransform.

Thanks!

Gabby

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