Re: [Algorithms] approximation to pow(n,x)?

[Simon F. <sim...@po...>]

Jon Watte wrote:
> Nathaniel Hoffman wrote:
>> lowly cosine power - it's not completely physically meaningless. If
>> you are using Blinn-Phong (N dot H, which is much to be preferred
>> over original Phong - R dot L), then using a cosine power is
>> equivalent to 
>> 
> 
> Except you already have the reflection vector for your environment
> mapping, so why not re-use it? 
> 

Ignoring any issues on what is more "physically accurate", I always
assumed that Blinn introduced his model because if you..

A) assume your view angle didn't change (i.e. viewer is an infinite
distance away) and
B) your lights are 'parallel/infinitely far away'

...then the method is much cheaper than the "Phong" method. 

I think these sort of assumptions are valid approximations for software
rendering, which was the norm at the time. Once these restrictive
conditions are lifted however, it seems to me that the original Phong
method is far cheaper.

Simon