[Bf-cycles] Improving OSL support

Fri Mar 14 18:11:41 CET 2014

Thanks for your input brecht.
will draft my proposal soon.

On Fri, Mar 14, 2014 at 6:01 AM, Brecht Van Lommel <
brechtvanlommel at pandora.be> wrote:

> Hi,
>
> On Mar 13, 2014 11:29 PM, "Naman Gupta" <naman22forever at gmail.com> wrote:
> > 1). metadata:- A possible way to do it would be to define our own
> keyword say  "meta". that works like this
> >
> >    int value =  4  meta range 0 10 tip "value betwwe 0-10",
> >
> >  something of that sort. but i'm not sure if acceptable since it would
> violate OSL coding standard.
>
> This is already a metadata feature in OSL with [[ ... ]] syntax, see the
> OSL specification. But we don't use the data at the moment.
>
> > 2). as for the texture. I think OSL already supports it without having
> to define another node altho that can also workout.
> >      https://www.youtube.com/watch?v=V5N2rnFtSlw
> >   can't really figure out what is exactly needed in this.
>
> This is about attributes being available. Like UV coordinates or vertex
> colors. In your example you didn't use those so you didn't see the problem.
> The attributes are currently only available if another node requests them.
>
> > 3). Performance improvement:- I think that's the thing we should be
> focusing on. A possible way to do that would be to allow OSL to use GPU
> along with CPU. it could be achieved using CUDA/OpenCL/OpenGL calls.
>
> GPU support for OSL would be great but I don't think it's possible as a
> summer of code project. It's too much work.
>
> What I was thinking of is simpler: faster handling of ShaderData end
> closures copying, faster image texture lookup, faster attribute lookup, and
> just generally comparing performance with the other shading system and
> finding solutions for differences in performance.
>
> > Apart from these issues I can't really find any other feature that needs
> to be added to OSL. If there is please do let me know.
> > Would like to know if i'm heading right.
>
> A few other things would be support for enums, better support for strings
> / file paths, support for image datablocks, support for curve mappings and
> color ramps. Better reporting of error messages and print statements in
> scripts, an option to print OSL and OpenImageIO statistics, or viewport
> auto update as you type. Support for shading in trace() function.
>
> A big feature would be the ability to implement own closures in OSL, but
> this is probably too complex and is more work in OSL than in Cycles.
>
> > Oh and one thing. I was able to build Blender with OSL under Release
> mode. Debug mode somehow crashes everytime.
> >
> > --Naman
> >
> >
> >
> >
> >
> >
> > On Fri, Mar 7, 2014 at 11:50 PM, Brecht Van Lommel <
> brechtvanlommel at pandora.be> wrote:
> >>
> >> Hi,
> >>
> >> On Fri, Mar 7, 2014 at 9:23 AM, Naman Gupta <naman22forever at gmail.com>
> wrote:
> >> > I'm Naman, final year undergrad majoring in Computer Science studying
> at
> >> > MIET, Meerut, India.
> >> > I'm interested in working for blender this summer. I'd like to work
> on OSL
> >> > support . What I can makeout from the idea page is that, blender
> doesn't
> >> > have all the features of OSL. like metadata, a proper way to load tex
> coord?
> >> > and improved performance?
> >> >
> >> > These are the links I have read so far
> >> >
> http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/OSL
> >> >
> https://raw.github.com/imageworks/OpenShadingLanguage/master/src/doc/osl-languagespec.pdf
> >> >
> >> >   I have successfully compiled the source code with OSL (win7,
> vs2008). :D
> >> >   I'd like to know who be the right guy(IRC handle?) to discuss it.
> >> >   Also, are there any other material that I have to go through?
> >>
> >> There's a few people on IRC that know about OSL integration, me
> >> (brecht), DingTo, lukas_t and dfelinto. You can ask here on the
> >> mailing list as well if you can find the right people online.
> >>
> >> I think you found the most important links. The other relevant things
> are:
> >> * Cycles developer docs:
> >> http://wiki.blender.org/index.php/Dev:2.6/Source/Render/Cycles
> >> * Rest of the Cycles manual.
> >> * To see what people are doing with OSL now you can read the OSL forum
> >> on http://blenderartists.org/
> >> * http://www.openshading.com/
> >>
> >> In general it helps if you are familiar with rendering algorithms as
> >> you can find in e.g. the PBRT book, though it's not that much needed
> >> for OSL.
> >>
> >> As for the contents of the project, the general goal would be to
> >> improve OSL integration to be more useful.
> >>
> >> * The metadata support would to make it possible to define
> >> input/output socket entirely from the metadata in the OSL shader
> >> (min/max, tooltips, strings as filepaths, etc.).
> >> * The texture loading problem is that Cycles will only load e.g. UV
> >> maps if they are needed by the nodes. However OSL shaders have no way
> >> to specify in advance that they will use such an attribute, so they
> >> can only use it if some other builtin node already asked for it to be
> >> loaded. I'm not sure what the best solution would be, but this should
> >> be solved somehow.
> >> * When using OSL performance is currently slower than when it's off,
> >> ideally it would become roughly equal. Getting it equal may be aiming
> >> a too high, but we can probably do better than we do now.
> >>
> >> Maybe other people reading this can suggest things, or you can read
> >> the blenderartists forum to find issues that users are running into
> >> and think of solutions for them. The 3 things mentioned are not
> >> necessarily the most important ones, just some things that I could
> >> think of off the top of my head.
> >>
> >> Brecht.
> >> _______________________________________________
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> >> Bf-cycles at blender.org
> >> http://lists.blender.org/mailman/listinfo/bf-cycles
> >
> >
> >
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