GeoServer WMS SLD scale rules causing boundaries to disappear near globe horizon in Cesium

GeoServer GeoServer User
1

Hello everyone,

I am using GeoServer WMS layers in Cesium (Cesium for Unreal Engine style globe rendering) to display political boundaries on a 3D globe.

Currently I have two boundary datasets:

  • Country boundaries

  • State boundaries

Both are served from GeoServer as WMS and consumed in Cesium using a single WebMapServiceRasterOverlay.

Goal

I want:

  • Country borders visible at large zoom level

  • State borders visible at low zoom level

So I attempted to use SLD scale rules with MaxScaleDenominator.

Example idea:

  • Countries: visible at larger scales (zoomed out)

  • States: visible only at smaller scales (zoomed in)

Problem

When using MaxScaleDenominator in the SLD for the state layer, I observe that borders disappear around the horizon of the globe.

Near the center of the screen, borders appear correctly, but near the edges / horizon of the globe the borders are missing.

This seems to happen because GeoServer calculates scale based on the tile BBOX, while Cesium renders a 3D globe where the same tile can represent vastly different scales depending on distance from the camera.

As a result, the scale used for rule evaluation sometimes exceeds the MaxScaleDenominator, and GeoServer stops rendering the borders for that tile entirely.

Constraints

There are a few constraints I cannot change:

  1. I must use only a single Cesium WMS raster overlay (cannot create multiple overlays).

  2. I want countries and states to appear at different zoom levels.

  3. I cannot refresh or recreate the WMS overlay dynamically because it causes visible flickering and looks bad.

  4. Stroke width cannot be less than 1 (so hiding with extremely thin strokes is not reliable).

  5. Borders should remain visible across the entire globe including near the horizon.

Current Approach

Using SLD rules like:

<?xml version="1.0" encoding="UTF-8"?>

<sld:StyledLayerDescriptor xmlns:sld="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" version="1.0.0">
  <sld:NamedLayer>
    <sld:Name>StateBoundary</sld:Name>
    <sld:UserStyle>
      <sld:FeatureTypeStyle>
        <sld:Rule>
          <sld:MaxScaleDenominator>3.0E7</sld:MaxScaleDenominator>

          <sld:LineSymbolizer>
            <sld:Stroke>
              <sld:CssParameter name="stroke">#FFFFFF</sld:CssParameter>

              <sld:CssParameter name="stroke-opacity">1.0</sld:CssParameter>

              <sld:CssParameter name="stroke-width">1.0</sld:CssParameter>

              <sld:CssParameter name="stroke-dasharray">6.0 3.0</sld:CssParameter>
          
        </sld:Stroke>
      </sld:LineSymbolizer>
      
    </sld:Rule>
  </sld:FeatureTypeStyle>
</sld:UserStyle>
  </sld:NamedLayer>
</sld:StyledLayerDescriptor>

This works near the camera but fails near the horizon.

BorderNotVisibleOnTheEdges
BorderNotVisibleOnTheEdges3840×2160 455 KB

BorderVisibleInTheCenter
BorderVisibleInTheCenter1920×1080 257 KB

Any suggestions or examples from similar setups would be greatly appreciated.

Thank you!