On 11/29/2016 3:26 PM, clipka wrote:
> Luminance gets a bit more complicated: You have to use an atan-based
> formula to get an angle, but you must plug in the y coordinate and the
> distance between the y axis; the latter is equal to sqrt(x*x+z*z), so
> this gives you:
>
>     #declare fL = function(x,y,z) { atan2(sqrt(x*x+z*z),y)*CONST }
>
> Choose CONST values as needed; atan2()*CONST may happen to be replacable
> by atan2d() again.
>

Wikipedia says it should be more like

	#declare fL = function(x,y,z) { atan2(sqrt(x*x+y*y+z*z),y)*CONST }

Do you agree?

Mike

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