Text from a KML/vector layer is not correctly rendered in 3D mode

[jmgomezpoveda]

Text defined in the style of items in a vector layer is not correctly rendered when in 3D mode.

• The text appears much larger compared to the feature images than it was in 2D mode.
• The text appears behind the feature images, so it can only be partially seen (this is critical when the text may just be one or two digits).

[gberaudo]

Do you have a screenshot?

[jmgomezpoveda]

Screenshots attached. This is the same map, just enabling the 3d mode.

[gberaudo]

Text style is handled in src/featureconverter.js, in olcs.FeatureConverter.prototype.olGeometry4326TextPartToCesium.

For having texts above the circles, there is the https://cesiumjs.org/Cesium/Build/Documentation/Label.html?classFilter=label#eyeOffset property in Cesium.

[jmgomezpoveda]

The vectors sample shows the same issue as above (text labels are too big and behind the feature), plus an additional issue, that letter within a piece of text are not vertically aligned (some letters are higher than others).

[gberaudo]

Regarding the size of the text, there is certainly some adjustement we should do.
Regarding alignment, it may be related to CesiumGS/cesium#3166
Regarding order, maybe we could put an eyeoffset: https://cesiumjs.org/Cesium/Build/Documentation/Billboard.html#eyeOffset.

[jmgomezpoveda]

Indeed, the alignment issue seems to be the one reported in CesiumGS/cesium#3166.

On the order, as per the documentation, eyeOffset seems to move the billboard in the y axis, but does not seem to change the z order.

As a workaround I was thinking more along the lines of defining the style as two separate styles for the image and the text, hoping that one will be drawn after the other, though I am not sure if that is supported by style functions.

[gberaudo]

The documentation example is: b.eyeOffset = new Cartesian3(0.0, 8000000.0, 0.0); which moves in the y direction. Having non zero value for z will move in the z direction.

[jmgomezpoveda]

As suggested, adding options.eyeOffset = new Cesium.Cartesian3(0.0, 0.0, -5.0); to olGeometry4326TextPartToCesium solves the issue with the z-order. Though, that -5 seems a bit arbitrary (I have tried smaller values, -1 and -2, and in those cases the text was still behind the polygon). Should I send a PR?

[gberaudo]

I don't see an easy and general way to handle this. So I would skip the PR for the moment.

[jmgomezpoveda]

Ok, let me know if you have any other ideas or you want me to test anything.