In article <web.3fbb761a1a62f81dd18b58c00@news.povray.org>,
 "Omega" <nomail@nomail> wrote:

> In the sinusoidal shadow one.. it was said that true diffraction effect
> cannot be achieved by PovRay.. that's what made me thought that it can't be
> done..

Right, diffraction can't be achieved. However, diffraction only accounts 
for a small part of point spreading.


> I grab pictures with a camera/lens assembly of a particular object. Since
> the lens is not perfect, it has a transfer function, the point-spread
> function (PSF) which causes high-intensity pixels to blur its surrounding
> neighbors.

Ok, this is "blooming", scattering/diffusion within the film or charge 
overflow in the CCD. This kind of scattering would be possible to 
simulate as a 2D convolution blur in the case of film, and a more 
complex blur for CCDs.

I'm pretty sure point spreading due to imperfect optics would require 
photon mapping with models of the actual optics, and is probably outside 
the capability of POV-Ray (unless you implement it as a POV script, in 
which case it will be very difficult and horribly slow and inefficient).


> Since I'm trying to simulate reality, I'm trying fo find a way, in PovRay,
> to generate this effect.
> 
> For now, I'm simulating the effect by doing a convolution with a
> user-defined kernel on my "hand"-simulated images.
> 
> Since I'm relatively new to PovRay3.5, I don't really know how to do it.

POV-Ray really isn't designed for this kind of image processing, but you 
can do something similar by loading the image as an image_map pigment, 
using functions to operate on each channel individually, and then using 
an average pigment with the channel functions to recombine them into one 
image. Alternatively, output in a form that POV-Ray's file I/O can read, 
and write a POV script that reads the image, processes it, and writes 
the blurred version out. You're really better off doing it in another 
program...

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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