[Sidefx-houdini-list] Shading artifact when really close to surface

guillaume laforge guillaume at alamaison.fr
Wed Oct 21 13:02:30 EDT 2009


It works :)

I tried to add and tweak randomly different combination but didn't get the
good one.

Is there any doc about all those dicing parameters ?

Thanks a lot Francois !!!

Cheers

Guillaume

On Wed, Oct 21, 2009 at 6:48 PM, Francois Duchesneau <sidefx at trinix.ca>wrote:

> If you add the vm_measure to your object and set it to "Uniform
> Measuring", the problem goes away. It's probably less efficient because it
> will have to dice too much far away.
>
> Let's hope it won't introduce artifacts elsewhere.
>
> François
>
> > My scene is just a sphere :).
> >
> > For info, here is a sample file showing the problem :
> > http://www.vol2nuit.fr/repro_shading_pb.hip
> >
> > Cheers
> >
> > Guillaume
> >
> > On Wed, Oct 21, 2009 at 4:01 PM, Francois Duchesneau
> > <sidefx at trinix.ca>wrote:
> >
> >> In that case what I don't understand is if I'm creating a sphere with a
> >> radius of 1 with a close up camera aiming at the top of the sphere, I
> >> won't get artifacts.
> >>
> >> This means there's must be something in particular that causes this. In
> >> my
> >> case all the fractured piece of geometries were separated. Is your
> >> sphere
> >> made up of different polygons not fused together?
> >>
> >> François
> >>
> >>
> >> > Hi François,
> >> >
> >> > Thanks for the info on your similar experience !
> >> >
> >> > I tried to scale down all except the camera but it doesn't solve the
> >> > problem
> >> > :-/.
> >> >
> >> > Btw, it is using 9.5.310. Didn't try in 10 yet.
> >> >
> >> > Cheers
> >> >
> >> > Guillaume
> >> >
> >> > 2009/10/21 François Duchesneau <sidefx at trinix.ca>
> >> >
> >> >> I ran into similar issues too.
> >> >>
> >> >> I wanted to render a pre-fractured ground with camera projection but
> >> >> many artifacts were visible around the seams. After many hours of
> >> >> research I tested the same in Maya and it worked so I decided to test
> >> it
> >> >> with Ray Tracing in Mantra and like you the problem disappear. My
> >> >> geometry had a big scale too and was also tangent to the camera.
> >> Maybe
> >> >> there are some tesselation settings out there in the properties to
> >> try
> >> >> out.
> >> >>
> >> >> I thought it might be an issue with micro-polygon but honestly I'd be
> >> >> surprised RenderMan had the same issue. Unfortunately I don't have it
> >> to
> >> >> test it.
> >> >>
> >> >> Out of curiosity, I guess if you recreate that kind of render in a
> >> >> smaller scale with a non-scaled camera you won't find any artifact.
> >> I'm
> >> >> asking because one day I had to scale a whole scene including the
> >> camera
> >> >> and a volume and I had to increase the volume sample a lot to make it
> >> >> render at a reasonable time.
> >> >>
> >> >> Good luck and let me know if you find anything.
> >> >>
> >> >> François
> >> >>
> >> >> guillaume laforge wrote:
> >> >> > Hi,
> >> >> >
> >> >> > I've got some shading artifacts when using micropolygon rendering
> >> with
> >> >> a
> >> >> > camera really close to a geometry.
> >> >> > The camera is tangent to the surface of a sphere. The sphere radius
> >> is
> >> >> 6371
> >> >> > unit with a white lambert shader.
> >> >> > When the camera distance to the surface is around four units, some
> >> >> patterns
> >> >> > appeared in the shading of the sphere.
> >> >> > At a distance of one unit, it is really "bumpy" !
> >> >> > If I'm rendering polygons as subdivision surfaces it is worst (and
> >> >> when
> >> >> need
> >> >> > to render this way).
> >> >> > If I increase the shading quality, it is worst too.
> >> >> > If I switch to Raytracing renderer, the problem disappear.
> >> >> Unfortunately
> >> >> we
> >> >> > need to use Micorpolygon Rendering for this project.
> >> >> >
> >> >> > I tried to scale down all the scene but it doesn't work. I guess
> >> the
> >> >> problem
> >> >> > came form the ratio between sphere radius and camera/surface
> >> distance
> >> >> being
> >> >> > too big...
> >> >> >
> >> >> > Is there any magic settings to remove this kind of artifact, or is
> >> it
> >> >> a
> >> >> > precision limitation of the micropolygon system.
> >> >> >
> >> >> > Thanks for any advice,
> >> >> >
> >> >> > Cheers.
> >> >> >
> >> >> >
> >> >> _______________________________________________
> >> >> Sidefx-houdini-list mailing list
> >> >> Sidefx-houdini-list at sidefx.com
> >> >> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >> >>
> >> > _______________________________________________
> >> > Sidefx-houdini-list mailing list
> >> > Sidefx-houdini-list at sidefx.com
> >> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >> >
> >>
> >>
> >> _______________________________________________
> >> Sidefx-houdini-list mailing list
> >> Sidefx-houdini-list at sidefx.com
> >> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >>
> > _______________________________________________
> > Sidefx-houdini-list mailing list
> > Sidefx-houdini-list at sidefx.com
> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >
>
>
> _______________________________________________
> Sidefx-houdini-list mailing list
> Sidefx-houdini-list at sidefx.com
> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>



More information about the Sidefx-houdini-list mailing list