public void setFillValue(float fillValue) {
        this.fillValue = fillValue;
        if (material != null) {
            material.setFloat("FillValue", fillValue);
        }
    }
Sets line/paper color ratio for areas with values less than luminance5,
really dark areas get no lines but a filled blob instead

@param fillValue the desired ratio (default=0.9)
jme3-effects/src/main/java/com/jme3/post/filters/CrossHatchFilter.java