The 3Delight Hair material is a physically plausible shader that renders hair and fur using a Monte-Carlo simulation. A Monte-Carlo simulation explores the different light paths inside a medium (in this case, a clump of hair) to produce an image. An interesting aspect of hair rendering is that all the intricate visual details seen in hair stem from the scattering of light in a multitude of hair strands and is not due to the complexity of the BRDF on a single hair strand. This seemingly simple observation explains why so many complex shaders are not successful at conveying a realistic look for hair. This includes the widely used shaders based on the Marschner model not using volume scattering. Below are four example renders of varying hair color. Note the glow caused by light scattering inside blond and light coloured red hair. Also note how black hair has nice silky features. The "glint" is caused by caustics inside hair strands and is not an after thought of the shading model. All theses features necessitate proper simulation of light scattering in hair clumps. |