On 2 May 2000 23:16:20 -0400, ron### [at] povrayorg (Ron Parker)
wrote:

>On Tue, 02 May 2000 20:48:21 -0500, Chris Huff wrote:
>>Stuff I don't know how to implement, and don't think I can figure out, 
>>but which I think is useful, information on these would be welcome:
>>    emboss
>
>This is a matrix function, as long as you do it along one of the eight
>multiples of 45 degrees.  For the usual "light in the upper left corner"
>effect, I believe the operation is
>  
> -1 0 0
>  0 1 0   * .5 + .5
>  0 0 0 

The numbers in the matrix above are correct. I'm not sure about the
multiplier and offset modifiers. For me, a vaue of one for the
multiplier works, and the offset value should be set to one-half of
the maximum possible value. I just tested these, and they work.

>>    sharpen_edges, and other "sharpen" filters. Blurring is pretty easy 
>>to figure out, but doing the opposite has me lost.

One type of sharpen filter:

-2      -2      -2

-2      32      -2

-2      -2       -2

Division Factor = 16
Bias, or Offset = 0



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