[Sidefx-houdini-list] Curves normals

Szymon Kapeniak szymon.kapeniak at gmail.com
Sat Aug 28 09:53:58 EDT 2010


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.

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
>>>>>>> _______________________________________________
>>>>>>> Sidefx-houdini-list mailing list
>>>>>>> Sidefx-houdini-list at sidefx.com
>>>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> --
>>>>>> =======================================
>>>>>> Andrew D Lyons | Digital Artist | http://www.tstex.com
>>>>>> =======================================
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>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
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