[Bf-committers] compositor defocus node

Ian Failing hemihuman at gmail.com
Sat Oct 23 00:58:37 CEST 2010

Jeroen, in re "What is the use of these blur types?" These blur types
emulate this visual effect of lensing:
Note the octagonal shape of the blurred lights in the second image, caused
by the shape of the aperture. The result of the effect is more noticeable
with small intense light sources on a dark background. This image is an
example of a "pixel that is more blurred and lays farther away, [that] can
effect a pixel that is more in front" (as bright blurry spots can "bleed
through" or "bend around" occluding objects), and should be a part of an
algorithm that tries to replicate lensing.

Christopher: (I assume you're not talking about some bug that doesn't befall
me.) I'm not an expert with this, but I think that physically accurate rack
focusing is only reasonably possible with a raytracing renderer that
simulates an aperture -- not something that Blender currently does. The
Blender renderer models an infinitely small aperture and throws out surfaces
that are occluded behind other objects, so it doesn't know what light would
be "showing through" the foreground object in order to properly blur its
inner edge. Maybe the non-depth-aware blurring could be improved somehow, I
don't know.


On Fri, Oct 22, 2010 at 2:21 PM, Christopher Cherrett <
ccherrett at openoctave.org> wrote:

>  While the defocus node is getting some attention I would like to point
> out that rack focusing with defocus does not work well. Objects jump in
> and out of focus with hard edged lines on the blur.
> -------- Original Message  --------
> Subject: [Bf-committers] compositor defocus node
> From: Jeroen Bakker <j.bakker at atmind.nl>
> To: bf-blender developers <bf-committers at blender.org>
> Date: 10/22/2010 10:09 AM
> > Hi All,
> >
> > I have reverse engineered the compositor defocus algorithm to its purest
> > form. the result I have posted on my blog.
> >
> >
> http://sicg.atmind.nl/index.php?option=com_content&view=article&id=29:blender-defocus-algorithm
> >
> > The current implementation is not depth aware. I am not sure that this
> > is a real issue, as nobody complains. I am also not sure about the many
> > filter types and settings. the circle has a faster algorithm then the
> > rest of the filters, but visually they do not differ much.
> >
> > Hope it is helpful to you all. Btw I am pleased with the speedup (50% on
> > my system). Will try on a GTX200 series next week.
> >
> > Cheers,
> > Jeroen
> > _______________________________________________
> > Bf-committers mailing list
> > Bf-committers at blender.org
> > http://lists.blender.org/mailman/listinfo/bf-committers
> --
> Christopher Cherrett
> ccherrett at openoctave.org
> http://www.openoctave.org
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