[Sidefx-houdini-list] Curves normals

Pablo Giménez pablogipi at gmail.com
Fri Sep 3 06:43:50 EDT 2010


2010/9/3 Olex P <hoknamahn at gmail.com>:
> I think answer is pretty simple - kd-tree gives better performance when it's
> built while BVH has better construction time. So probably in general
> performance gain is given by faster raytracing than by faster building of
> acceleration structures. BVH is better in interactive applications where
> construction time is more important.
thanks for the clarification
>
> 2010/9/3 Pablo Giménez <pablogipi at gmail.com>
>
>> 2010/8/31 Olex P <hoknamahn at gmail.com>:
>> > Hey Pablo,
>> >
>> > Was it you asking about IPR and fur rendering? Something about IPR
>> getting
>> > stuck on the kd tree generation stage. Could you try the same scene but
>> with
>> > BVH (ta-dam we have it now!) instead of kd tree (Mantra ROP, Rendering
>> tab,
>> > Ray Tracing Accelerator parameter). Construction of BVH should be way
>> faster
>> > than of kd tree plus it could be less expensive in terms of memory
>> > consumption. Maybe it could solve your problem.
>> Yes it i much faster, actually makes raytracing with hair usable for me.
>> Thanks!
>> One thing I have read the docs about vm_octreestyle, but is still not
>> clear why BVH is not the degault octree style rather than KD-Tree, in
>> other words ,are there adventages of KD-Tree over BVH?
>> >
>> > 2010/8/31 Pablo Giménez <pablogipi at gmail.com>
>> >
>> >> 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
>> >> >>>>>>>> _______________________________________________
>> >> >>>>>>>> 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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>> >> >>>>>>>
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>> >> >>>>>>>
>> >> >>>>>>>
>> >> >>>>>>>
>> >> >>>>>>
>> >> >>>>>>
>> >> >>>>>>
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>> >> >>>>>
>> >> >>>>>
>> >> >>>>
>> >> >>>>
>> >> >>>>
>> >> >>>
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>> >> >>
>> >> >>
>> >> >>
>> >> >> --
>> >> >> No, I am not on Facebook.
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>> >> >>
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>> >>
>> >>
>> >>
>> >> --
>> >> Un saludo
>> >> Best Regards
>> >> Pablo Giménez
>> >> _______________________________________________
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>> >>
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>>
>>
>>
>> --
>> Un saludo
>> Best Regards
>> Pablo Giménez
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-- 
Un saludo
Best Regards
Pablo Giménez



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