[Sidefx-houdini-list] Curves normals

Pablo Giménez pablogipi at gmail.com
Fri Sep 3 05:35:04 EDT 2010


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
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>> >>>>>>>> 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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>> >>>>
>> >>>>
>> >>>>
>> >>>
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>>
>>
>> --
>> Un saludo
>> Best Regards
>> Pablo Giménez
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-- 
Un saludo
Best Regards
Pablo Giménez



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