[Bf-committers] Opensubdiv and catmull-clark again

Yury Baranov cucumberer at gmail.com
Fri Nov 6 12:14:58 CET 2015 

Sergey,
OK, if I understand correctly, creases handling is not a part of the
Catmull-Clark algo. But I'll catch the moment and ask to implement GUI for
some OSD features:
1. UV subdivision options
2. Chaikin rule for creases (really nice feature!)
3. Triangle subdivision rule

This features are mentioned in Pixar OSD reference manual[1].
And again, thanks for everything you do for Blender!

[1] http://graphics.pixar.com/opensubdiv/docs/subdivision_surfaces.html

2015-11-06 10:33 GMT+03:00 Mike Erwin <significant.bit at gmail.com>:

> Cool, I just opened OpenSubdiv issue #757 for adaptive tessellation on
> Intel.
>
> Also have an open bug in Apple's bug tracker, re-reported as OpenSubdiv
> issue #758.
>
> Mike Erwin
> musician, naturalist, pixel pusher, hacker extraordinaire
>
> On Fri, Nov 6, 2015 at 1:12 AM, Sergey Sharybin <sergey.vfx at gmail.com>
> wrote:
>
> > Issues with upstream development branch of OpenSubdiv are to be reported
> to
> > their github tracker [1].
> >
> > We will go to latest OpenSubdiv as soon as i catch up with real life
> after
> > all this flying. Hopefully for the Monday-Tuesday we'll have updated libs
> > for all the supported platforms.
> >
> >
> > [1] https://github.com/PixarAnimationStudios/OpenSubdiv/issues
> >
> > On Fri, Nov 6, 2015 at 11:03 AM, Mike Erwin <significant.bit at gmail.com>
> > wrote:
> >
> > > Hi Sergey!
> > >
> > > I wasn't suggesting the latest OSD should have been rushed into 2.76.
> But
> > > definitely for the next update. I've upgraded Blender to OSD 3.0.3
> > locally
> > > and it fixes GLSL compute for both AMD and Intel on Windows. Adaptive
> > > subdivision doesn't seem to work on Intel chips -- on Windows or Mac --
> > > even with Pixar's example programs. No crash or errors; the surface
> just
> > > doesn't appear on screen. Non-adaptive works fine.
> > >
> > > How soon can we bump the libs to 3.0.3? I have a few changes to the
> > > Blender-OSD glue. Can those go into master or would you prefer a new
> > branch
> > > for the stuff I'll be working on?
> > >
> > > No ideas yet for the normals but I will investigate. As you know we're
> > > moving to GLSL 1.5 soon so rewriting is going to happen anyway.
> > >
> > > Mike Erwin
> > > musician, naturalist, pixel pusher, hacker extraordinaire
> > >
> > > On Thu, Nov 5, 2015 at 11:22 PM, Sergey Sharybin <sergey.vfx at gmail.com
> >
> > > wrote:
> > >
> > > > Yury,
> > > >
> > > > For the original mail: OpenSubdiv and Blender original CCGSubSurf are
> > > using
> > > > different approaches to the patch topology construction, but both of
> > them
> > > > technically are Catmull-Clark subdivisions. There's no correct or
> wrong
> > > > crease here, it's just different and behaves better in one situation
> or
> > > > another. We'll switch to OpenSubdiv completely once all the issues
> are
> > > > solved.
> > > >
> > > > For the followup mail: you're pointing out all the TODOs and
> > limitations
> > > > mentioned in the original release page [1]. Don't see much reason to
> > > > discuss them here, we'll need to work on this still. With a project
> > size
> > > of
> > > > OpenSubdiv and the tight release schedule we had so far you can't
> > really
> > > > have everything to be ideally supported from the first commit. It'll
> > all
> > > > come eventually.
> > > >
> > > > Mike,
> > > >
> > > > GLSL Compute is disabled for AMD devices because original OSD library
> > we
> > > > used for the 2.76-rc1 had a bug on AMD hardware. It was fixed later
> at
> > > rc2
> > > > or rc3 from the OpenSubdiv side, but we can't bump library versions
> at
> > > the
> > > > RC stage (bumping it will mean we're allowing to use hardware which
> was
> > > > known to be buggy without too much tests done first).
> > > >
> > > > For the shading, here's the bug report [2]. I didn't find a way to
> > > evaluate
> > > > limit surface on the GPU when using non-adaptive subdivisions and i
> > > didn't
> > > > really heard back from Pixar about how it could be done. Wold need to
> > ask
> > > > the guys again. But OpenSubdiv 3.0 is quite fresh so far and perhaps
> > > > non-adaptive case is not high priority for them yet.
> > > >
> > > > Perhaps we can do some other trickery to get better normals, but
> that'd
> > > > requite having tessellation control and evaluation shaders which was
> > > quite
> > > > hard to do with current OpenGL state we've got. It didn't quite work
> > for
> > > me
> > > > when trying to sue it as an #extension for glsl 1.3 and mumping glsl
> to
> > > 1.4
> > > > and higher would mean re-writting all the existing shaders (due to
> > > removed
> > > > of loads of deprecated stuff in it, i.e. gl_Normal). Maybe you can
> have
> > > > some other ideas here tho.
> > > >
> > > > [1]
> > > >
> > http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.76/OpenSubdiv
> > > > [2] https://developer.blender.org/T45707
> > > >
> > > >
> > > >
> > > > On Thu, Nov 5, 2015 at 10:02 PM, Mike Erwin <
> significant.bit at gmail.com
> > >
> > > > wrote:
> > > >
> > > > > Hi guys,
> > > > > I'm actively working on OpenSubdiv, especially getting it running
> on
> > > more
> > > > > systems (Intel gfx on Windows, Mac). GLSL compute works on the
> latest
> > > > > version of OSD (official Blender release doesn't use this yet).
> > Similar
> > > > > performance to Transform Feedback. The other problems you
> mention...
> > > yep
> > > > > those are still problems.
> > > > >
> > > > > Thanks for pointing out #2 -- I knew it looked odd but didn't make
> > the
> > > > > connection to low-poly normals. Can you give a link to the bug
> > tracker?
> > > > >
> > > > > From my understanding, OpenSubdiv will become *the* subsurf
> > > > implementation
> > > > > in Blender, and the old system will go away. But first we need to
> fix
> > > > these
> > > > > problems.
> > > > >
> > > > > Mike Erwin
> > > > > musician, naturalist, pixel pusher, hacker extraordinaire
> > > > >
> > > > > On Thu, Nov 5, 2015 at 7:52 AM, Yury Baranov <cucumberer at gmail.com
> >
> > > > wrote:
> > > > >
> > > > > > Opensubdiv is unusable ATM in fact. Problems are:
> > > > > > 1. Unable to apply Subsurf with OSD enabled. Result is identical
> to
> > > > > Subsurf
> > > > > > without OSD check.
> > > > > > 2. Shading is wrong (bug is in the bugtracker already). OSD takes
> > > > normals
> > > > > > for shading from lowpoly instead of computing new normals.
> > > > > > 3. No UV subdivision.
> > > > > > 4. GLSL Compute is not working for me.
> > > > > > OK, the feature is too new and too raw to use it in production.
> But
> > > OSD
> > > > > is
> > > > > > based on Catmull-Clark algo, which is already used in the Subsurf
> > > > > modifier,
> > > > > > OSD is just speeding mesh calculation up. The problem is, OSD and
> > > > > > Catmull-Clark subdiv models look different, it not supposed to
> > happen
> > > > > IMHO.
> > > > > >
> > > > > > 2015-11-05 15:33 GMT+03:00 Nahuel Belich <
> > casillapforos at yahoo.com.ar
> > > >:
> > > > > >
> > > > > > > intersting, in that case, as a modeler i would prefer the open
> > subv
> > > > > > > result, however i didnt model that much using it, the
> performance
> > > its
> > > > > > much
> > > > > > > much better, but the shading its "weird" or not accurate on
> most
> > > > cases.
> > > > > > . .
> > > > > > >  i need to test it more to shape an opinion
> > > > > > > PasteAll.org - opensubdiv.jpg
> > > > > > > |   |
> > > > > > > |   |   |   |   |   |
> > > > > > > | PasteAll.org - opensubdiv.jpgPasteAll.org - opensubdiv.jpg
> > > > > > > opensubdiv.jpg ~0.11mb..ish. 916 px. 1335 px. |< << hi
> > PasteAll.org
> > > > is
> > > > > > > brought to you by the monkeys of GraphicAll.org -  |
> > > > > > > |  |
> > > > > > > | Ver en www.pasteall.org | Vista previa por Yahoo |
> > > > > > > |  |
> > > > > > > |   |
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >      El Jueves, 5 de noviembre, 2015 5:09:30, Yury Baranov <
> > > > > > > cucumberer at gmail.com> escribió:
> > > > > > >
> > > > > > >
> > > > > > >  Hi. I just mentioned that Blender's subdivision surface is
> > acting
> > > a
> > > > > > little
> > > > > > > bit different than opensubdiv. It's noticable when using
> creases
> > on
> > > > > > > geometry like this: http://puu.sh/la3Xw/3c06b8b687.png
> > > > > > > Blender's catmull-clark subdivs:
> > > http://puu.sh/la3ZJ/a5f8ce2ddf.png
> > > > > > > Opensubdiv: http://puu.sh/la40E/529b72bec5.png
> > > > > > >
> > > > > > > Looks like Blender's Catmull-Clark subdivs are not
> Catmull-Clark
> > > > > > subdivs...
> > > > > > > _______________________________________________
> > > > > > > Bf-committers mailing list
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> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > _______________________________________________
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> > > >
> > > >
> > > >
> > > > --
> > > > With best regards, Sergey Sharybin
> > > > _______________________________________________
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> >
> >
> >
> > --
> > With best regards, Sergey Sharybin
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