Models 2D/CV support

[bagnell]

Adds support for rendering models in 2D and Columbus view. Model.minimumPixelSize is not supported.

The only thing is changed is the computed model matrix. If the model is supposed to be deformed in 2D like other geometry, then the vertices need to be projected to 2D and this can be closed.

[pjcozzi]

I know this is private, but is it worth writing a unit tests for?

[bagnell]

This was moved from Camera that has a bunch of tests to make sure camera reference frames work in all scene modes. I'll add a couple of explicit tests though.

[pjcozzi]

Add a unit test for rendering in 2D and in CV.

[pjcozzi]

Update CHANGES.md.

[pjcozzi]

Can you check all the Sandcastle examples with scene3DOnly: true. Perhaps the development on and CZML examples?

[pjcozzi]

They are all OK.

[pjcozzi]

Model.minimumPixelSize is not supported.

OK with me, but update it's doc to state that.

[pjcozzi]

What's the plan for depth testing?

[pjcozzi]

Part of #927.

[pjcozzi]

Also add info to the Model constructor function about the precision. This is fine for small models (it would be good if you can define-ish this), but only the origin takes into account the projection so each vertex in the model is slightly off, and more off as it goes away from the origin. For example create a box that is a million meters using a glTF model and Cesium geometries, and they will be in two different places since the later correctly projects all vertices.

[pjcozzi]

I imagine implement this will be non-trivial? It doesn't need to be part of this PR, but we could also fade it out/in.

[bagnell]

Model.minimumPixelSize is not supported.

OK with me, but update it's doc to state that.

minimumPixelSize now works.

[pjcozzi]

minimumPixelSize now works.

Cool! Let me know when this is ready for another review.

@mramato let us know if you convert the demo CZML.

[mramato]

[pjcozzi]

As discussed offline, let's detect when the model crosses the IDL and draw in both viewports.

[pjcozzi]

@bagnell let's aim to ship this for Cesium 1.22. Is there anything else needed besides #3764 (comment)?

[bagnell]

@pjcozzi The z-fighting mentioned in #3764 (comment) is still an issue. We discussed a couple ways to fix it offline that I haven't tried yet.

[pjcozzi]

@bagnell is this ready for a final review and merge since #3953 was merged?

[bagnell]

Yes, this should be good to go. The only change in this branch that wasn't reviewed or in the z-fighting or IDL PRs was some test fixes.

[pjcozzi]

Make the minimum pixel size 800 and infinite 2D goes away. Is this because the model's bounding sphere is so big?

var viewer = new Cesium.Viewer('cesiumContainer', {
    infoBox : false,
    selectionIndicator : false
});

function createModel(url, height) {
    viewer.entities.removeAll();

    var position = Cesium.Cartesian3.fromDegrees(-179.0744619, 44.0503706, height);
    var heading = Cesium.Math.toRadians(135);
    var pitch = 0;
    var roll = 0;
    var orientation = Cesium.Transforms.headingPitchRollQuaternion(position, heading, pitch, roll);

    var entity = viewer.entities.add({
        name : url,
        position : position,
        orientation : orientation,
        model : {
            uri : url,
            minimumPixelSize : 800,
            //maximumScale : 20000
        }
    });
    viewer.trackedEntity = entity;
}

var options = [{
    text : 'Aircraft',
    onselect : function() {
        createModel('../../SampleData/models/CesiumAir/Cesium_Air.glb', 5000.0);
    }
}, {
    text : 'Ground vehicle',
    onselect : function() {
        createModel('../../SampleData/models/CesiumGround/Cesium_Ground.glb', 0);
    }
}, {
    text : 'Milk truck',
    onselect : function() {
        createModel('../../SampleData/models/CesiumMilkTruck/CesiumMilkTruck-kmc.glb', 0);
    }
}, {
    text : 'Skinned character',
    onselect : function() {
        createModel('../../SampleData/models/CesiumMan/Cesium_Man.glb', 0);
    }
}];

Sandcastle.addToolbarMenu(options);

[pjcozzi]

The tests pass and all the code looks good. Just that comment.

[pjcozzi]

Turns out I was in CV.