backgroundColor = new GradientColorValue();
Color color = Color.valueOf("878787");
backgroundColor.setColors(new float[] { color.r, color.g, color.b});
models = new Array<Model>();
ModelBuilder builder = new ModelBuilder();
Model xyzModel = builder.createXYZCoordinates(10, new Material(), Usage.Position|Usage.ColorPacked),
planeModel = builder.createLineGrid(10, 10, 1, 1, new Material(ColorAttribute.createDiffuse(Color.WHITE)), Usage.Position);
models.add(xyzModel);
models.add(planeModel);
xyzInstance = new ModelInstance(xyzModel);
xzPlaneInstance = new ModelInstance(planeModel);
xyPlaneInstance = new ModelInstance(planeModel);