[Sidefx-houdini-list] Curves normals

Pablo Giménez pablogipi at gmail.com
Fri Aug 27 09:58:37 EDT 2010


Yes definitely seems to be a bug in H11.0.446.9 , yes you got it is
the current production version!
Latest daily build work well and creates the s coordinate properly.
H10 also works fine.
Just in case somebody else is havign a similar problem.

2010/8/26 Louis Dunlevy <louisdunlevy at gmail.com>:
> parametric s should not be zero. If it is, I'm thinking it may be a bug
>
> On 27/08/10 03:02, Pablo Giménez wrote:
>> Hi Andrew.
>> I have done similar things for other stuff, but my problem is that the
>> s coordinate is constant 0 for all the points in the curve geometry.
>> The t is fine, going from 0 to 1 along the curve lenght, but s is
>> supposed to be along the curve "cross sections" width, and this is not
>> happening.
>> With a proper s coordinate along the width of the curve would be easy
>> to fake a rounded look.
>> cheers
>>
>> 2010/8/26 Andrew D Lyons<tstexture at gmail.com>:
>>
>>> I did this recently to generate fur sprites. If you get the curve
>>> tangent and stack some cross products with another version of the
>>> curve with normals hard coded to point towards the camera (or some
>>> cardinal axis) then you should be able to derive a normal that is
>>> always pointing in a general direction - but which follows the
>>> contours of the curve.
>>>
>>> 2010/8/26 Pablo Giménez<pablogipi at gmail.com>:
>>>
>>>> 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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>>>>
>>>>
>>>
>>>
>>> --
>>> =======================================
>>> Andrew D Lyons | Digital Artist | http://www.tstex.com
>>> =======================================
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>>>
>>>
>>
>>
>>
>
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-- 
Un saludo
Best Regards
Pablo Giménez



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