[Sidefx-houdini-list] Curves normals

Pablo Giménez pablogipi at gmail.com
Tue Aug 31 05:28:51 EDT 2010


2010/8/28 Szymon Kapeniak <szymon.kapeniak at gmail.com>:
> 2010/8/28 Peter Bowmar <pbowmar at gmail.com>:
>> Indeed, there is a new property that turns on/off shading curves as
>> surfaces. I don't remember what it's called though...
>
> ..."vm_curvesurface" as mentioned previously, but as far as I
> understand Pablo's problem was, that even with this property turned
> on, early build of Mantra H11 didn't create "s" variable for hair (I
> can't verify this though). With H11.0.485 all seems to be fine.
Yes, that was the problem, but now seems to be working in latest daily built.
>
> Anyhow, this optimization is interesting, I made some test renders
> yesterday comparing H10 and H11 with Marschner, Arno Zinke nad
> Houdini's default textured hair shaders. It seems to work well both
> for rendering speed and memory footprint but also has a huge impact on
> fur quality in a middle to close-up shots. No elliptical hairs shape,
> flat less vivid speculars, less distinctive hairs in a far field
> scenario.
>
>
>
>
>>
>> On 28 August 2010 01:34, Louis Dunlevy <louisdunlevy at gmail.com> wrote:
>>> actually I betcha it's just a new default rendering parameter for that
>>> optimisation that was mentioned earlier, you can probably switch it back
>>> to the old method..
>>>
>>> On 08/28/10 00:58, Pablo Giménez wrote:
>>>> 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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>>>>
>>>>
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>>
>>
>> --
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-- 
Un saludo
Best Regards
Pablo Giménez



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