Today, the shading method of Phong plays an important role in the design of real-time image generation systems. Often, the model has been used in combination with a colour interpolation, suppressing a main property of this model, namely the visually acceptable rendering of highlights. Unfortunately, Phong's algorithm demands a normalisation step, which is expensive to implement in hardware. We will present several shading methods which are reductions of the Phong algorithm. They will be compared both visually and theoretically. The alternatives are judged with respect to their hardware implementation cost. The result is a hierarchy of shading methods that can be used to select the required cost-performance ratio for a given visualisation task.