[Sidefx-houdini-list] Curves normals

Andrew D Lyons tstexture at gmail.com
Thu Aug 26 16:54:20 EDT 2010


Ah ok,

There's some of that in here:

http://code.google.com/p/cortex-vfx/

So I'm guessing Dr D at least have taken that approach...

Cheers


On 26 August 2010 13:46, Craig Hoffman <craigleehoffman at aol.com> wrote:
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>  Not really- that is a big custom programming effort unloading calculations onto GPUs- I am just talking about using standard game technology inside of a 3D package to speed up visualization of large complex scenes.  Basically we are already setting up our complex scenes to do instancing at render-time, so why not do the same thing using the GPU so we can interact with it?  Obviously it can't be as complex, but it would be great to be able to show thousands (or tens of thousands) of instanced feathers (scattered points with GPU instanced geometric strips with textures and GL shader on them) on a bird character in your viewport and interact quickly with it with no slowdown (unlike what would happen if we created them all with a COPY SOP), and then hit the 'Render' button and have the proper hi-res feathers be instanced at render time by Mantra.
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> -Craig
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> -----Original Message-----
> From: Andrew D Lyons <tstexture at gmail.com>
> To: sidefx-houdini-list at sidefx.com
> Sent: Thu, Aug 26, 2010 1:08 pm
> Subject: Re: [Sidefx-houdini-list] Curves normals
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>
> Something like this?
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> http://www.vizworld.com/2010/01/nvidia-weta-collaborate-create-pantaray/
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> Cheers
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>
> On 26 August 2010 12:34, Craig Hoffman <craigleehoffman at aol.com> wrote:
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>>  I think this is exactly what OpenGL instancing would be good with- creating
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> tons of geometry on the fly on the GPU without the hit of being created on the
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> CPU and pushed over the bus.  Basically you create an object like a tree or a
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> feather and a parent surface like a ground or bird with points scattered on it
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> (like you would for the Fur Procedural) then the GPU copies the one tree or
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> feather to each point you have scattered on the surface and point attributes on
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> the scattered points are used to drive variety in the hardware render using
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> OpenGL shaders.
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>> We should be able to see and interact with large systems of
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> fur/forest/feathers/grass/city buildings/etc. (albeit simpler lower resolution
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> versions of them perhaps) with modern hardware than we currently can.  Houdini
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> has the instancing and geometry shader paradigm setup already and that just
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> needs to be supported in OpenGL also- I hope Houdini can be a leader in this
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> arena as it would open up a lot of capabilities for a lot of things.  (But the
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> geometry shader thing would only work on the latest DX11/OGL4.0 graphics cards,
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> although the instancing and hardware rendering stuff will work with the older
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> cards).
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>> -Craig
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>> -----Original Message-----
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>> From: Alex Czetwertynski <alex at franktheplumber.com>
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>> To: <sidefx-houdini-list at sidefx.com> <sidefx-houdini-list at sidefx.com>
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>> Sent: Thu, Aug 26, 2010 11:21 am
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>> Subject: Re: [Sidefx-houdini-list] Curves normals
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>> Ah that makes sense.  Haven't played with hair in Houdini yet.
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>> With particles though I find it difficult to visualize the scale of the width
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>> attribute, even though I do see the points.  I'm sure this will come in handy
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> at
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>> some point
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>> On Aug 26, 2010, at 11:18 AM, Pablo Giménez wrote:
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>>> 2010/8/26 Alex Czetwertynski <alex at franktheplumber.com>:
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>>>> How about creating so low res geo to preview what you are doing?  Or do you
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>>>> just get to used to knowing what you are doing you don't even need that
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>>>> anymore :)
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>>> You have particles points and heirs guide lines as a preview.
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>>> In this case my filaments are created from poly lines that exists in
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>>> you scene and you visualize in the viewport. So you are not absolutely
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>>> blind.
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>>>>
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>>>>
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>>>> On 8/26/10 11:13 AM, "Pablo Giménez" <pablogipi at gmail.com> wrote:
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>>>>
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>>>>> 2010/8/26 Alex Czetwertynski <alex at franktheplumber.com>:
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>>>>>> I have recently been wondering about this a lot as I have the same
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> question
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>>>>>> related to particles.
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>>>>>> If Houdini is creating this geometry at render time, wouldn't it make
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> sense
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>>>>>> to give the user some kind of representation of what is going on in OpenGL
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>>>>>> land?  It feels like some remnant of pre-graphics card days where you need
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>> to
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>>>>>> do this blindfolded somehow to not create too much geometry in the
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>> viewport.
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>>>>>>  What is the rationale for keeping these kinds of workflows?
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>>>>> Because that would create looooots of geometry, which can be created
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>>>>> at render time and then be much more eficcient.
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>>>>> We are talking about order of millions in point rendering and fur/heir
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>>>>> in production.
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>>>>>>
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>>>>>> Sorry if this is an obvious question, I'm migrating to Houdini from apps
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>>>>>> where you barely ever have to deal with this kind of stuff
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>>>>>>
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>>>>>> Thanks
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>>>>>> Alex
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>>>>>>
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>>>>>> On Aug 26, 2010, at 8:05 AM, Pablo Giménez wrote:
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>>>>>>
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>>>>>>> Hi.
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>>>>>>> I am rendering some poly lines as curves, using the 'width' attribute
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>>>>>>> to control every filament width.
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>>>>>>> That's all right.
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>>>>>>> Problem is that this geometry is created at render time and the
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>>>>>>> normals and texture coordinates are a little bit odd.
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>>>>>>> My main problem is that Mantra creates the needed geometry using the
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>>>>>>> width attribute but seems that is only shading the original curve
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>>>>>>> attributes.
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>>>>>>> I mean the hair geometry is created extendin the shaded point,
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>>>>>>> perpendicular to the point of view, and the new geo seems to use the
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>>>>>>> same shading as the original point.
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>>>>>>> Is similar to what happens with points rendering, where the point is
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>>>>>>> shaded once, and then all the geometry created at render time around
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>>>>>>> the origian lpoint use the same shading from the original one.
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>>>>>>> So you don't have proper normals to make for instance a diffuse
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>>>>>>> lighting that gives you some "rounded" look.
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>>>>>>> I have tried the hairNormalVOP, creating my own tangents, created
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>>>>>>> texture coordinates with s going along the hair line from 0 to 1, but
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>>>>>>> the normals I got are just pointin towards camera, they are not doing
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>>>>>>> the "Rounding2 effect that is suppose to do this operator.
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>>>>>>> So is there any way to go away from the planar look of curves shading,
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>>>>>>> any way to have sense whre you shading point is in the new created
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>>>>>>> gemetry so you can for instance fake normals o apply any othe rtrick.
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>>>>>>> Thanks
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>>>>>>> --
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>>>>>>> Un saludo
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>>>>>>> Best Regards
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>>
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>>>>>>> Pablo Giménez
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>>
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>>>>>>> _______________________________________________
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>>
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>>>>>>> Sidefx-houdini-list mailing list
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>>
>
>>>>>>> Sidefx-houdini-list at sidefx.com
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>>
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>>>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
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>>
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>>>>>>
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>>
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>>>>>> _______________________________________________
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>>
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>>>>>> Sidefx-houdini-list mailing list
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>>
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>>
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>>>>>>
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>>>>>
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>>>>>
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>>>>
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>>>> _______________________________________________
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>>
>
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>>>>
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>>>
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>>>
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>>>
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>>> --
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>>
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>>> Un saludo
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>>
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>>> Best Regards
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>>
>
>>> Pablo Giménez
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>>
>
>>> _______________________________________________
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>>
>
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> --
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> =======================================
>
> Andrew D Lyons | Digital Artist | http://www.tstex.com
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