[Sidefx-houdini-list] Curves normals

Alex Czetwertynski alex at franktheplumber.com
Thu Aug 26 14:21:27 EDT 2010


Ah that makes sense.  Haven't played with hair in Houdini yet.
With particles though I find it difficult to visualize the scale of the width attribute, even though I do see the points.  I'm sure this will come in handy at some point


On Aug 26, 2010, at 11:18 AM, Pablo Giménez wrote:

> 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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>>>>> Sidefx-houdini-list at sidefx.com
>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>> 
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>> 
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> 
> 
> 
> -- 
> Un saludo
> Best Regards
> Pablo Giménez
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