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

[Leonardo E. Segovia]

Hey all,

Brecht: sadly, it is expected. I did more tests and it turns out that
multiplying Radial Roughness by 3 gets a more similar look to the "before"
render. Now, I think it'll be better to start separating the render into
modes to see where the noise is actually coming from.

Best regards,
Leonardo

El mié., 25 de jul. de 2018 a la(s) 09:45, Brecht Van Lommel (
brechtvanlommel at gmail.com) escribió:

> 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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> 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
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