Polygons on terrain

[pjcozzi]

This is @bagnell's polygon on terrain work-in-progress. Part of #2172.

It is not ready to be reviewed.

We opened this pull request so we can coordinate testing it the algorithm.

TODO:

• Documentation
• Tests

[pjcozzi]

@bagnell can you add a TODO list to this pull request, e.g., jitter on zoom out, texturing, and other things you are still working?

[pjcozzi]

Zoomed in, looking straight down, the multifrustum artifact can be minor:

Or major:

[pjcozzi]

Here is the viewer is not in the volume, but a near plane intersects it. The artifact in the upper-left slides across the screen as we zoom in:

until is appears OK:

Zooming in a bit farther creates the artifact you mentioned to me offline, but I don't think the viewer is inside the volume. It looks like it is capturing the terrain skirts (perhaps of the farther frustum?):

[pjcozzi]

Unrelated to polygons on terrain, I get a lot of false collision detection when zooming into Mount St. Helen's that causes the camera to bounce. We could fix it in a separate PR if it is easy or submit a new issue.

[pjcozzi]

RE: inside volume issue:

I think this is only inside the first frustum, that is why we see the skirts of the second frustum. Use the Cesium Inspector to Show globe depth to see what I mean.

[pjcozzi]

Well, maybe it is always the first frustum, but this view has two frustums and they are both wrong:

[pjcozzi]

Set debugVolume to true. Perhaps the vertex shader near plane clamping is wrong as you mentioned offline?

Here is a similar view to the above screenshot but showing the volume:

It might be a bit easier to visualize if we could toggle this on/off and optionally depth test it.

[pjcozzi]

Is there anywhere else you think we could be missing a stencil clear?

[pjcozzi]

Another way to track this down is to debug with only a single view frustum. This doesn't have as many artifacts, but still has the same problem when the view is inside the volume and starts to look up.

Try this code:

//Create the viewer.
var viewer = new Cesium.Viewer('cesiumContainer');
var scene = viewer.scene;
scene.terrainProvider = new Cesium.CesiumTerrainProvider({
    url: '//cesiumjs.org/stk-terrain/tilesets/world/tiles',
    requestVertexNormals : true
});
scene.globe.depthTestAgainstTerrain = true;

var positions = [new Cesium.Cartesian3(-2358138.847340281, -3744072.459541374, 4581158.5714175375),
                 new Cesium.Cartesian3(-2357231.4925370603, -3745103.7886602185, 4580702.9757762635),
                 new Cesium.Cartesian3(-2355912.902205431, -3744249.029778454, 4582402.154378103),
                 new Cesium.Cartesian3(-2357208.0209552636, -3743553.4420488174, 4581961.863286629)];

var polygonHierarchy = { positions : positions };

var groundPolygon = scene.primitives.add(new Cesium.GroundPolygon({
    debugVolume : true,
    polygonHierarchy : polygonHierarchy
}));

viewer.scene.farToNearRatio = 100000000.0;

viewer.camera.lookAt(new Cesium.Cartesian3(-2354331.3069306486, -3742016.2427205616, 4581875.591571755), new Cesium.HeadingPitchRange(Cesium.Math.toRadians(20.0), Cesium.Math.toRadians(-35.0), 10000.0));
viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);

viewer.extend(Cesium.viewerCesiumInspectorMixin);

Sandcastle.addToolbarButton('Toggle', function() {
    groundPolygon.debugVolume = !groundPolygon.debugVolume;
});

Then hit the Toggle button to see how the debug volume shading changes when the polygon disappears:

[bagnell]

@pjcozzi This is ready for another look.

[pjcozzi]

Add these new functions to CHANGES.md.

[pjcozzi]

In Firefox only, picking is inconsistent. Check out the blinking when mousing over the green rectangle:

[mramato]

In Firefox only, picking is inconsistent.

This isn't specific to this branch/polygons, see #2942

[pjcozzi]

The GroundPrimitive tests fail in IE. Can we just bail on them when we don't have stencil bits?

We should also make this more clear in the Sandcastle example.

[pjcozzi]

That's all. This is basically ready.

[bagnell]

Can we just bail on them when we don't have stencil bits?

I checked the spec and depth-stencil renderbuffers must be supported. If you go to the picking Sandcastle example, it still works with a depth-stencil renderbuffer attachment.

The reason it fails in IE is because we need the EXT_frag_depth extension. I added a check to the tests that render.

[bagnell]

@pjcozzi This is ready.

[bagnell]

@pjcozzi I added an isSupported function like we talked about offline. This is now ready.

[pjcozzi]

Amazing.

[nmschulte]

Where's the +1 button? 👍

[pjcozzi]

@bagnell can you merge master into 3d-tiles and fix the conflicts in Primitive.js and PolygonGeometry.js? The conflict in Scene.js is just: