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Quadratic shading and its hardware implementation

Abbas A. M., Szirmay-Kalos L., Horvath T., Foris T.

Machine Graphics and Vision

2000

Vol. 9, No. 4

825-839

Rendering systems often represent curved surfaces as a mesh of planar polygons that are shaded to restore a smooth appearance. Gouraud shading uses linear color interpolation and its hardware implementation is relatively easy, but it handles specular highlights incorrectly and introduces annoying artifacts called Mach banding over the edges of the polygon mesh. In software rendering, Phong shading has been more popular, because it can realistically handle specular materials. Since it requires the rendering equation to be evaluated for each pioxel, its hardware support poses problems. This paper presents a nonlinear, i.e. quadratic interpilation scheme which is in between Gouraud shading and Phong shading. It can also be implemented by hardware means as Gouraud shading, but its shading quality is comparable with that of the Phong shading. A software simulation and VHDL description of the shading hardware are also presented.

Reflectance models by pumping up the albedo function

Neumann L., Neumann A., Szirmay-Kalos L.

Machine Graphics and Vision

1999

Vol. 8, No. 1

3-17

The paper introduces a method, called the albedo pumping-up, to derive new, physically plausible BRDFs from an axisting one or from any symmetric function. This operation can be applied recursively arbitrary number of times. An important application of this operation is the transformation of the Phong and Blinn models in order to make them produce metallic effects. The paper also examines the albedo function of reflectance models and comes to the conclusion that widely used models violate energy balance at grazing angles.