@Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule c = ex.getCapsule(this);
        c.write(gridTileLoader, "terrainQuadGrid", null);
        c.write(size, "size", 0);
        c.write(patchSize, "patchSize", 0);
        c.write(stepScale, "stepScale", null);
        c.write(offset, "offset", null);
        c.write(offsetAmount, "offsetAmount", 0);
        c.write(material, "material", null);
    }
This will print out any exceptions from the thread
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainGrid.java