[Bf-cycles] Sample filtering options

[Matthew Heimlich]

I did a quick B-H implementation based on Lux's code a while back. I'll
post here if I can find the file.

On Thu, Aug 6, 2015 at 1:06 PM, Mohamed Sakr <3dsakr at gmail.com> wrote:

> I will add the Blackman-Harris soon once I have a free 2 days.
>
> On Thu, Aug 6, 2015 at 6:33 PM, Brecht Van Lommel <
> brechtvanlommel at pandora.be> wrote:
>
>> I strongly suggest to not add any pixel filters with negative weights
>> to Cycles, like Catmull-rom, Sincor Lanczos. In my opinion they only
>> add problems and I would not suggest anyone to use them in practice.
>> Blackman–Harris could be good to add, since that's a filter with
>> positive weights that supposedly has less ringing than Gaussian. But
>> it's the only one I can think of.
>>
>> With a path tracer like Cycles there's enough AA samples that you
>> don't need to artificially sharpen the image, and deal with problems
>> like ringing or clamping negative values. I think it's a legacy
>> feature that is no longer needed. The large filter collections offered
>> by renderers was never useful in my opinion, it's just needless UI
>> complexity, most of the filters are just not good.
>>
>> Also note that denoising algorithms work best with filter importance
>> sampling since all the pixels are then decorrelated. So if a denoiser
>> is implemented at some point it would be simplest if it just worked
>> with all filters.
>>
>>
>> On Thu, Aug 6, 2015 at 5:12 PM, Nathan Vegdahl <cessen at cessen.com> wrote:
>> > Yes, I am talking about pixel/sample/AA filters.  Look up the paper
>> "Filter
>> > Importance Sampling" for more information.
>> >
>> > As for texture filtering, I'm sure there's more flexibility there, as
>> I'm
>> > pretty sure it uses more standard techniques.
>> >
>> > --Nathan
>> >
>> > On Aug 6, 2015 8:08 AM, "Yury Baranov" <cucumberer at gmail.com> wrote:
>> >>
>> >> Hi,
>> >> I was talking about other filters (maybe they called AA filters). There
>> >> are two of them ATM: Box and Gaussian. And Bitmap filters are Smart,
>> Cubic,
>> >> Closest and Linear.
>> >>
>> >> 2015-08-06 18:01 GMT+03:00 Nathan Vegdahl <cessen at cessen.com>:
>> >>>
>> >>> IIRC Cycles uses "filter importance sampling" to do its sample
>> filtering.
>> >>> This has some advantages, but one of its disadvantages is that it
>> doesn't
>> >>> work well with filters that have negative lobes (the resulting
>> renders are
>> >>> very noisy).
>> >>>
>> >>> All the filters you mention have negative lobes, so although they
>> >>> technically could be implemented, my guess is that they won't be.  It
>> would
>> >>> be very unexpected behavior to a user if they switched filters and
>> suddenly
>> >>> their image was twice as noisey.
>> >>>
>> >>> --Nathan
>> >>>
>> >>> On Aug 6, 2015 7:38 AM, "Yury Baranov" <cucumberer at gmail.com> wrote:
>> >>>>
>> >>>> Hi. Is it planned to make more sample filtering options like
>> >>>> catmull-rom, sinc, lanczos etc.? Maybe more filtering options for
>> bitmaps
>> >>>> will be good, too.
>> >>>>
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