Am 04.08.2016 um 16:18 schrieb udyank:
> I have some doubts on how the defocus module is actually working. On which plane
> is the jittering of rays happening? And how is it able to produce realistic
> images without the concept of a lens?

I presume you're talking about focal blur.

In POV-Ray, focal blur is implemented by jittering the actual origin of
the rays vertically and horizontally perpendicular to the camera axis,
typically in a circular region. At the same time, the direction of the
rays is adjusted in the opposite direction, so that each ray still
passes through the same point on the plane of sharpness that it would
have passed through without the jittering.

To compare this with a real camera lens, the camera location can be
thought of as the center of the diaphragm (or, more precisely, the
diaphragm's virtual image as seem through the lens), and the jittering
of the rays accounts for the fact that the diaphragm's aperture is not
infinitesimally small.

Virtually the only difference to the image of a real camera lens is that
POV-Ray's algorithm by default results in a perfectly circular and
uniform bokeh (provided you use high enough focal blur quality
settings), while the bokeh of real camera lenses often approaches that
of a polygon, and in special lense types may even be somewhat circular
or even non-uniform in brightness. To mimick such effects, POV-Ray
provides the `bokeh` camera setting, which lets you use a pattern to
define the shape of the aperture.

> And also, the POVRay doc on the aperture setting says that "the zone of
> sharpness is a plane through the focal_point and is parallel to the camera". How
> is that? Is the plane is along depth(Z), ie horizontal, or parallel to camera
> (vertical) ?

The zone of sharpness is a plane. As such, it is /both/ horizontal /and/
vertical, parallel to the camera [image], or in other words
perpendicular to the camera axis.

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