The object is from the Stanford Scanning Repository. Experiment with Contour Enhancing Lines shading. A distant mask was rendered from the dragon to make a 16-bit greyscale terrain. It is lit by a parallel light with infinite width. The terrain got a texture, or not. Above at right it is transparent with a refraction index below 1 and the WpH76_SC250_800 HDRI generates negative light to create the colours. This method gives nice black contours and renders in around 5 seconds.