[Soc-2018-dev] Weekly report #10 - Implementing a Hair Shader for Cycles

Brecht Van Lommel brechtvanlommel at gmail.com
Wed Jul 25 14:44:58 CEST 2018


Thanks for the tests. To me the before renders still look better? While 3x
gives similar noise levels, the results are less accurate, the hair is
noticeably brighter.

On Tue, Jul 24, 2018 at 10:40 PM Leonardo E. Segovia <
leonardo.segovia at cs.uns.edu.ar> wrote:

> Hey all, hi Brecht,
>
> As regards noise and fireflies, they come from basically two places:
> - Low Roughness. This compress (longitudinally) the glints so much, they
> look like fireflies.
> - Low Radial Roughness. These make the hair look SO soft!
> - Very lightly colored hair (this one is non fixeable by us)
>
> Possible mitigations include:
> - Raising the clamp from 0.001 to 0.01 to at least have a reasonable glint
> when Roughness < 0.1
> - Filter Glossy
>
> I've already uploaded a fix for the former. I'd like to discuss the
> behavior of Filter Glossy.
>
> When doing the CPU profiling that you requested, I realised that Filter
> Glossy is executed after the closure setup (before closure setup =
> roughness, after = logistic parameters), which means it isn't affecting the
> roughness properly.
> rB52a0e67fe005
> <https://developer.blender.org/rB52a0e67fe0050683a888d6643ec2035bd2b3ea1c>
> is the commit that includes both mitigations, however, the new
> implementation is noticeably less effective. I've obtained decent results
> when applying fmaxf(3*roughness to both Roughness and Radial Roughness;
> you'll find a visual comparison of the fixes below. (The original picture
> is up at https://framapic.org/ksZ7ftOaGvqk/gS2Cv0cjrdUg.jpg.)
>
>
>
> I'm not sure if there is any need to strengthen Filter Glossy wrt. Radial
> Roughness in this way; please let me know what you think.
>
> Best regards,
> Leonardo
>
> El lun., 23 de jul. de 2018 a la(s) 08:16, Brecht Van Lommel (
> brechtvanlommel at gmail.com) escribió:
>
>> Hi,
>>
>>
>>>    - The regression test suite has not been uploaded yet to SVN.
>>>
>>
>> I've committed these as well now.
>>
>>
>>>    - It's been asked in the BA thread if I have extra objectives for the
>>>    shaders. Do you feel that more features/controls should be added?
>>>
>>
>> More features could be good, but also part of the GSoC plan was to
>> investigate optimizations for the shader, since it still is relatively slow
>> / noisy.
>>
>> So I think you should at least profile the shader, and look into
>> fireflies to see where they come from and if they are expected or not. I
>> don't know if there is anything major to find, but it's worth investigating.
>>
>>       - I came up with controls for each of the modes (R, TT, TRT, TRRT+).
>>>       - It's been also suggested to prune the UI into a "Basic" and
>>>       "Advanced" mode.
>>>
>>
>> I'd be hesitant to add features to break physical correctness and energy
>> conservation so early, before people have really tested the shader. I
>> rather users test it and then give us feedback saying they can't achieve
>> this or that look, and then we see what the best solution is.
>>
>> Maybe commit it to your branch and then we can always add it later if
>> there is a need for it.
>>
>>
>>> About the GSoC project deliverables:
>>>
>>>    - If I read the mail correctly, Google wants us students to summarize
>>>    and show off our work in a single place e.g. a blog post. How does
>>> Blender
>>>    handle this?
>>>       - My preference would be to add a page (similar to when one
>>> publishes
>>>       a paper) in amyspark.me explaining the work we did. We could embed
>>>       the resulting pictures, credits, etc. and the demonstration video
>>> from
>>>       Youtube.
>>>       - As for "Get the code", perhaps I could add links to the relevant
>>>       commits?
>>>
>>
>> A webpage is fine, for the code you can link to the git branch.
>>
>> Thanks,
>> Brecht.
>>
>>
>> --
>> Soc-2018-dev mailing list
>> Soc-2018-dev at blender.org
>> https://lists.blender.org/mailman/listinfo/soc-2018-dev
>>
>
>
> --
> Lic. Leonardo E. Segovia
> Departamento de Ciencias e Ingeniería de la Computación
> Universidad Nacional del Sur
> San Andrés 800 - Campus Palihue, B8000 Bahía Blanca, Argentina
> --
> Soc-2018-dev mailing list
> Soc-2018-dev at blender.org
> https://lists.blender.org/mailman/listinfo/soc-2018-dev
>
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