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2018-06-28T21:24:04Z

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wiki>LeonardoSegovia: Forgot a couple parentheses when writing this

2018-05-25T19:59:20Z

Forgot a couple parentheses when writing this

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= Week 2 =

Hi everyone! The second week is gone, and this is my report.

== Objectives ==

With the shader in place, I could move on to the following (Weeks 4-5):

* Test shader functionality. If working, release test build.
* Evaluate received feedback. Start bug fixes.

== What's been done ==

Admittedly, not much 😢

<ul>
<li>Lukas added a Diffuse override for using the shader with non-hair geometry, in <code>bsdf_principled_hair_setup</code>. When using it with hair, however, Blender didn't render anything ''at all''. This was because the ID of the shader was outside the range of <code>CLOSURE_IS_BSDF</code>. Our shader is now treated as BSDF and transmissive ({{GitCommit|rBc4174a44dc311d2fd65ca74c4387bbc6f529df95}}).</li>
<li>With the BSDF in place, I tried to get reference renders. The main problem is that Blender's hair primitive is returning <code>NaN</code>s in any or all of the following:
<ul>
<li>the ray distance <code>t</code></li>
<li>the intersection calculation, somewhere deep within <code>cardinal_curve_intersect</code> or <code>curve_intersect</code></li>
<li>the curve distance <code>h</code> (this one usually comes from the above)</li></ul>

Which results in one or more of the following:
<ul>
<li>crash when integrating indirect radiance ("<code>Non-finite sum in path_radiance_clamp_and_sum!</code>")</li>
<li>crash when obtaining <code>azimuthal_scattering</code> (I have a scene to obtain this exact crash)</li>
<li><code>assert(fabsf(dot(sd->dPdu, dPdCD)) < 1e-5f);</code>. I do not know (yet) what this one means.</li></ul>

I ring-fenced the shader from most of those ({{GitCommit|rB92030f83362fe567f78e519e0acca0700287a933}}). Brecht agreed to have a look at those weird <code>NaN</code>s, since they come from outside our shader.</li>
<li>[https://developer.blender.org/T54796 In Phabricator's task for this project], Ronan Ducluzeau could get a reference render without crashing. The shader returns a lot of noise and fireflies.</li></ul>

== Next up ==

Once we figure out why we receive bogus data from the ray intersection (and fix it), I'll be able to continue revising the shader.

If possible, I'd like to get a dev build out in BlenderArtists for people to test. I don't expect to get great results yet, but it'd be great if we can ensure the hair primitive works properly. I don't have good enough bandwidth (3Mb) to upload a 200MB+ build unless I go to the uni, so I may ask either Lukas or bzztploink in IRC if they can upload them.

== Questions ==

* In re assertion above - what does it mean?
* What could be possible sources of noise in our shader? Compared with a Diffuse shader (which doesn't use the hair primitive data), it's obviously not working properly. I wonder if this and the other issues are related.

← 古い版	2018年6月28日 (木) 21:24時点における版
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利用者:LeonardoSegovia/GSoC 2018/Reports/Week 2 - 版の履歴

Yamyam: 1版 をインポートしました

wiki>LeonardoSegovia: Forgot a couple parentheses when writing this

Yamyam: 1版をインポートしました