[Bf-viewport] GLSL Node

Wed Jun 10 08:30:52 CEST 2015

Lots of discussion here, sorry I am a little slow to respond here.
Hopefully I hit most of the things covered so far:

Jacob, I am not sure what you are referring to with a core profile with
regards to shaders. There is an OpenGL core profile, but there is no point
in us restricting ourselves by following (better to use the compatibility
profile).

I certainly see GLSL node(s) being mixed with existing nodes. They would be
a great way to create utility nodes or otherwise allow users to patch gaps
in node system.

I agree that GLSL export would be a nice to have.

I am not sure about adding too many new nodes for things like branching and
looping. Mostly I am concerned about adding nodes that a renderer doesn't
actually use. I still don't see how that is intended to be handled.

I don't see much need for a wrapper language, we might as well use straight
GLSL. The inputs and outputs should be easy to parse, and is something we
already have if we are only looking at the in and out variables of
functions (as opposed to uniforms and in/out variables). We may add some
custom language things via pragmas, but that is likely as far as we would
go with any kind of custom language.

I am still a little confused about when the GLSL node will be available.
Mostly, what render engine needs to be selected in order to use it, or will
that selection even matter?

Regards,
Daniel

On Tue, Jun 9, 2015 at 4:10 AM, Khalifa Lame <khalibloo at gmail.com> wrote:

> Here's an idea then. Use a "wrapper language" like unity's shaderlab. this
> wrapper language can simply be a python class written by the user, that
> defines the input variables for the GLSL shader and their ui
> layout/representation.
>
> also, i think there should be a way to load in shader code from text files
> via the materials panel (without using nodes).
>
> as for the shader stages, what if we had "node subtrees"? the user selects
> the glsl node tree and then he has the option to select a vertex shader
> subtree or a fragment/tessellation subtree. the outputs from a vertex
> shader subtree for example, can be fed into the next subtree by simply
> declaring inputs with similar IDs.
>
> On Tue, Jun 9, 2015 at 11:07 AM, Antony Riakiotakis <kalast at gmail.com>
> wrote:
>
>> We already have a custom parser in gpu_codegen.c, see
>> gpu_parse_functions_string. This can be improved upon if needed.
>> I don't think loops or conditionals will complicate things but any "out"
>> variables of a shader function will need to be written to, to guarantee
>> there are no garbage values. But this will be up to the author of the
>> shader.
>>
>> On 9 June 2015 at 07:58, Olivier Parisy <olivier.parisy at gmail.com> wrote:
>>
>>> Well, didn't want to clutter the list, but since you're asking for a
>>> feedback... [image: ☺]
>>>
>>> My understanding is that this would be a productive, modern way to
>>> design GLSL shaders, due to an expressive combination of "classical" nodes
>>> and code fragments and real-time feedback. Very empowering, and I suppose
>>> this could even be used for postprocessings or, as a strech, "demo-like"
>>> oddities à la shadertoy.
>>>
>>> In this regard, being able to export generated GLSL code, even
>>> unoptimized (as is currently possible) would be a must.
>>>
>>> One question: do you feel control structures such as branching or loops
>>> would complicate matters? I suppose they would be a good use case for GLSL
>>> script nodes. Those nodes may also be a way to code shaders in a more
>>> modular way, without resorting to tricks such as a preprocessor.
>>>
>>> As already stated, automatic creation of typed inputs/outputs for those
>>> nodes will require some GLSL parsing capabilities. Does the blender code
>>> base already contain such a parser? If not, what is the preferred parsing
>>> strategy in blender? Grammars compilers / code generators? Ad-hoc,
>>> handcrafted ones?
>>>
>>> Regards,
>>> Olivier.
>>>
>>> Le lun. 8 juin 2015 23:59, Mike Erwin <significant.bit at gmail.com> a
>>> écrit :
>>>
>>>> Re: multiple shader stages
>>>>
>>>> Some of the wireframe shaders I prototyped are multi-stage, with work
>>>> split between vertex and fragment. So yes we'll need to do *at least*
>>>> those. Geometry stage in the near future or maybe for the initial release.
>>>> How do we visually designate stages in the UI, since as Daniel points out
>>>> most so far could be lumped into the fragment category?
>>>>
>>>> Here's what I see in my head:
>>>> Inputs to the vertex shader node come from geometry data source (as
>>>> attributes) or from other nodes (as uniforms). Inputs to the fragment
>>>> shader node come from vertex shader outputs directly or from other nodes
>>>> (again as uniforms). Use consistent input/output names and wires
>>>> automatically connect. So in the basic case we have 3 things wired
>>>> together: data source --> vertex --> fragment. Can't wait to see this on
>>>> screen!
>>>>
>>>> Does anyone else here envision mixing of the new GLSL shader nodes and
>>>> existing nodes?
>>>>
>>>> Watching the Guilty Gear Xrd presentation now...
>>>>
>>>> Mike Erwin
>>>> musician, naturalist, pixel pusher, hacker extraordinaire
>>>>
>>>> On Mon, Jun 8, 2015 at 5:00 PM, Antony Riakiotakis <kalast at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi Daniel,
>>>>>
>>>>> The idea is to make a new system that will be powerful enough allow
>>>>> the game engine to use it, but I expect the game engine to adapt to it
>>>>> rather than the opposite. The initial plan was to not have blender
>>>>> internal compatibility at all.
>>>>>
>>>>> The node system already has compatibility flags so nodes can set the
>>>>> engine(s) they are compatible with. I expect many existing nodes will
>>>>> need little modification to run on new OpenGL. Most of the code that
>>>>> needs to be changed is the uniform and attribute declarations and this
>>>>> is handled internally in the gpu_codegen module.
>>>>>
>>>>> For the script nodes, initial plan was to make a fragment shader node
>>>>> at first, but of course we should make it possible to hook more shader
>>>>> stages, perhaps by using many text data blocks on the node itself. If
>>>>> there are constraints that would be nice to have now would be the time
>>>>> to express them I guess. The problem of compatibility is again
>>>>> bypassed by ignoring it. Any shiny new shader nodes go only to new
>>>>> viewport. Obviously shader stages can only be executed in a system
>>>>> that supports them. Might be worth defining alternative node trees for
>>>>> system without some shader stages but this becomes too technical very
>>>>> quickly and can get out of hand.
>>>>> Let's focus on high level functionality first.
>>>>>
>>>>> For the material panel it's more of a UI issue. I agree it would be
>>>>> nice to expose an interface in a more meaningful way. I think node
>>>>> groups can give us some tools to optimize this workflow somewhat if we
>>>>> can expose their input interface in the material panel.
>>>>> _______________________________________________
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>>>>>
>>>>
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>>
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>
>
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> khalibloo®
>
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