[Sidefx-houdini-list] Curves normals

Pablo Giménez pablogipi at gmail.com
Thu Aug 26 14:18:39 EDT 2010


2010/8/26 Alex Czetwertynski <alex at franktheplumber.com>:
> How about creating so low res geo to preview what you are doing?  Or do you
> just get to used to knowing what you are doing you don't even need that
> anymore :)
You have particles points and heirs guide lines as a preview.
In this case my filaments are created from poly lines that exists in
you scene and you visualize in the viewport. So you are not absolutely
blind.
>
>
> On 8/26/10 11:13 AM, "Pablo Giménez" <pablogipi at gmail.com> wrote:
>
>> 2010/8/26 Alex Czetwertynski <alex at franktheplumber.com>:
>>> I have recently been wondering about this a lot as I have the same question
>>> related to particles.
>>> If Houdini is creating this geometry at render time, wouldn't it make sense
>>> to give the user some kind of representation of what is going on in OpenGL
>>> land?  It feels like some remnant of pre-graphics card days where you need to
>>> do this blindfolded somehow to not create too much geometry in the viewport.
>>>  What is the rationale for keeping these kinds of workflows?
>> Because that would create looooots of geometry, which can be created
>> at render time and then be much more eficcient.
>> We are talking about order of millions in point rendering and fur/heir
>> in production.
>>>
>>> Sorry if this is an obvious question, I'm migrating to Houdini from apps
>>> where you barely ever have to deal with this kind of stuff
>>>
>>> Thanks
>>> Alex
>>>
>>> On Aug 26, 2010, at 8:05 AM, Pablo Giménez wrote:
>>>
>>>> Hi.
>>>> I am rendering some poly lines as curves, using the 'width' attribute
>>>> to control every filament width.
>>>> That's all right.
>>>> Problem is that this geometry is created at render time and the
>>>> normals and texture coordinates are a little bit odd.
>>>> My main problem is that Mantra creates the needed geometry using the
>>>> width attribute but seems that is only shading the original curve
>>>> attributes.
>>>> I mean the hair geometry is created extendin the shaded point,
>>>> perpendicular to the point of view, and the new geo seems to use the
>>>> same shading as the original point.
>>>> Is similar to what happens with points rendering, where the point is
>>>> shaded once, and then all the geometry created at render time around
>>>> the origian lpoint use the same shading from the original one.
>>>> So you don't have proper normals to make for instance a diffuse
>>>> lighting that gives you some "rounded" look.
>>>> I have tried the hairNormalVOP, creating my own tangents, created
>>>> texture coordinates with s going along the hair line from 0 to 1, but
>>>> the normals I got are just pointin towards camera, they are not doing
>>>> the "Rounding2 effect that is suppose to do this operator.
>>>> So is there any way to go away from the planar look of curves shading,
>>>> any way to have sense whre you shading point is in the new created
>>>> gemetry so you can for instance fake normals o apply any othe rtrick.
>>>> Thanks
>>>> --
>>>> Un saludo
>>>> Best Regards
>>>> Pablo Giménez
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>>>
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>>
>>
>
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-- 
Un saludo
Best Regards
Pablo Giménez



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