On 11/9/2016 12:41 AM, clipka wrote:
> Am 09.11.2016 um 05:28 schrieb Mike Horvath:
>> http://wiki.povray.org/content/Reference:Camera#Focal_Blur
>>
>> The docs say, "The center of the zone of sharpness is specified by the
>> focal_point vector. The zone of sharpness is a plane through the
>> focal_point and is parallel to the camera. Objects close to this plane
>> of focus are in focus and those farther from that plane are more
>> blurred. The default value is focal_point<0,0,0>."
>>
>> How can a plane be parallel to the camera? Can't a plane only be
>> perpendicular to a vector?
>
> Interpret it as "parallel to the image plane" -- or, in other words,
> "perpendicular to the camera axis".
>
>> Also, I don't understand why a plane is used at all. All points
>> equidistant from focal_point should form a sphere, don't they?
>
> Uh, yes, technically, all points equidistant from _any_ given point form
> a sphere, but how would a sphere centered around focal_point (= an
> arbitrary point by which the location of the zone of sharpness is
> defined) be of any relevance?
>
> Presuming that you mean "all points equidistant from the camera
> location", the answer is: Yes, that would also be a sphere -- but the
> zone of sharpness in a normal camera is _not_ the set of points
> equidistant to the camera lens; rather, in a real-life camera it is the
> set of points equidistant to the image plane, and that's also the case
> for POV-Ray's camera.
>

Okay, thanks.

Mike

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