In the sole case of bumpmapping, i fail to understand why numerous people claim that Dot3 has superior quality to EVBM, but i fail to understand why-
Both can operate at the triangle level and linear interpolate 3 vectors::
For Dot3, the vectors are the tangent-space light direction.
For EVBM, the vectors are traditionally the model-space normal, but are more accurate if they are the model-space normal rotated into light space since you can’t represent a complete 3d rotation with the “2d Du/Dv matrix transform” that rotates the normal into light space.
Beyond that however, Dot3 only performs a dot-product and produces a single linear scalar that can be used in the classic 'lambertian equation of lighting.
However, EVBM uses a 2d texture lookup for the perturbed normal which can emulate the Dot3 effect by using a texture with the classic white to black falloff circle image that numerically simulates going from 0 to 1.
Yet, EVBM can make that falloff non-linear, can embed colors, can model anistropy, etc. It has much more potential by using that texture lookup instead of the unchangeable Dot3 math.
The 8/8bit Du/Dv perturbations or even the 5/5/6bit dU/dV/Luminance allow the same changes in shape to occur as a normal map.
Clearly adding EVBM is costly to hardware and performance (1 extra tex unit), but it has the potential to do the same things as Dot3 at greater precision (interpolating floats instead of +/-128 chars)
So does anyone know what am i missing?