Charcoal rendering and shading with reflections

In this work, we have developed an approach to include global illumination effects into charcoal drawing (see Figure 1). Our charcoal shader provides a robust computation to obtain charcoal effect for a wide variety of diffuse and specular materials. Our contributions can be summarized as follows: (1) A Barrycentric shader that is based on degree zero B-spline basis functions; (2) A set of hand-drawn charcoal control texture images that naturally provide desired charcoal look-and-feel; and (3) A painter's hierarchy for handling a high number of shading parameters consistent with charcoal drawing.