[Sidefx-houdini-list] Rendering boxes with cusped edges anddisplacements

Sean Lewkiw Sean.Lewkiw at cis-vancouver.com
Wed Aug 24 19:59:18 EDT 2011


True 'nuff, thanks for that tip too!

My new shader now has a fancy-schmancy dropdown to choose any one of these three methods.

I'm calling this the "Method Surface Discombobulator XV2000" and you will see a presentation at Siggraph next year.

thanks everyone.
Sean



-----Original Message-----
From: sidefx-houdini-list-bounces at sidefx.com [mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of Craig Hoffman
Sent: Wednesday, August 24, 2011 2:16 PM
To: sidefx-houdini-list at sidefx.com
Subject: Re: [Sidefx-houdini-list] Rendering boxes with cusped edges anddisplacements



If you just want a bumpy surface you don't have to displace along the normals.  You can displace in XYZ using the results from a 3D noise lookup (though you might need to normalize it to go from -1 to 1 in all dimensions).  Make sure you make the proper "REST" attribute for the lookup, etc.

I used to do this with Renderman in the old days and am assuming Mantra handles it fine...


Then again the extra attribute to drive the displacement as suggested below should work too.  You might need to make sure this attribute gets transformed as the object rotates, though, or you might get some sizzling in the bumps...

Cheers,
Craig








-----Original Message-----
From: Phil Spicer <PSpicer at bournemouth.ac.uk>
To: sidefx-houdini-list <sidefx-houdini-list at sidefx.com>
Sent: Wed, Aug 24, 2011 11:15 am
Subject: Re: [Sidefx-houdini-list] Rendering boxes with cusped edges anddisplacements


Hi Sean,

You clever man... it works really well, and makes a proper sugar cube
aesthetic...

Kind regards,

Phil.
________________________________________
From: sidefx-houdini-list-bounces at sidefx.com [sidefx-houdini-list-bounces at sidefx.com]
On Behalf Of Sean Lewkiw [Sean.Lewkiw at cis-vancouver.com]
Sent: 24 August 2011 18:49
To: 'sidefx-houdini-list at sidefx.com'
Subject: Re: [Sidefx-houdini-list] Rendering boxes with cusped edges
anddisplacements

Hm, that did something interesting, I'll keep investigating but it looks
promising.

I created the att that stored the smooth N, added the cusped vertex N, used my
att as the N input in "displace along N VOP" with "ensure proper smooth shading"
turned off, then added a "shading N" vop after the N output.  I get
displacement, cusped edge, and no tearing.

Sean



-----Original Message-----
From: sidefx-houdini-list-bounces at sidefx.com [mailto:sidefx-houdini-list-bounces at sidefx.com]
On Behalf Of Mark Elendt
Sent: Wednesday, August 24, 2011 9:23 AM
To: sidefx-houdini-list at sidefx.com
Subject: Re: [Sidefx-houdini-list] Rendering boxes with cusped edges
anddisplacements

The reason this happens is that you're likely displacing along the
normal.  Since the normals aren't smooth across the polygons, you end
up with a discontinuity (leading to cracks).

You might try creating a separate point attribute to represent the
smooth normals and using that to displace (rather than the shading
normal).

Hope that makes some kind of sense.

P.S.  Even with vertex normals, you'll get discontinuities in the displacement.

On Wednesday Aug 24 at 09:09, Sean Lewkiw wrote:
> Thanks for the suggestions guys... this does indeed work (subd or polybevel)
but it is not a practical solution in my case because I have tens of thousands
of these boxes to deal with.
>
> Sean
>
>
>
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com [mailto:sidefx-houdini-list-bounces at sidefx.com]
On Behalf Of Phil Spicer
> Sent: Wednesday, August 24, 2011 1:42 AM
> To: sidefx-houdini-list at sidefx.com
> Subject: Re: [Sidefx-houdini-list] Rendering boxes with cusped edges
anddisplacements
>
> Hi Sean,
>
> I gave the edges of the box a polybevel of 0.001 without cusping N, and it
gave me a bumpy box with no teared edges. Not an ideal solution I know, but the
noise passes through the edges in a pleasing way whilst retaining the overall
box aesthetic. It is not quite as boxy as a sugar cube however it is not that
far off.
>
> Kind regards,
>
> Phil.
>
>
>
>
>
>
> On 24 Aug 2011, at 03:39, Christopher Stewart wrote:
>
> > Sorry Sean, but this is great to hear. Thought I was just all
> > brainless and thumbs.
> >
> > I've been making all affected geometry sub-d's with hella-creased
> > corners. It fixes that and some other shading issues.
> >
> > Not any kind of real solution and hopefully somebody here knows the score...
> >
> > --
> > ----
> > Christopher Stewart
> > Vancouver, BC
> > 3D | VFX | IT
> >
> >
> >
> > On Tue, Aug 23, 2011 at 6:49 PM, Sean Lewkiw
> > <Sean.Lewkiw at cis-vancouver.com> wrote:
> >> I'm pulling my hair out trying to get this to work.
> >>
> >> I have a bog-standard box.  I apply a simple shader and render, I get
smoothed edges.  Slap on a vertex sop, cusp N, I get faceted edges.  Good.
> >>
> >> Apply a displacement using simple turbulent noise in a simple "material
shader builder" shader.  Now I get the sharp edges, but the displacement tears.
It looks the same as you get with a unshared points box, only there are no
holes.... the holes are just filled with a streaked displacement.
> >>
> >> Uncusp the vertex N, it looks nice, but now I have interpolated normals and
it no longer looks box-like and shades weirdly at edges.
> >>
> >> Am I asking for the moon on a stick to expect this to work?  I need the
non-interpolated normals of the cusped version, without the tearing of the
cusped version.
> >>
> >> Sean
> >>
> >>
> >>
> >>
> >>
> >> _____________________________________
> >> Sean Lewkiw | DFX Supervisor
> >> method studios vancouver || 50 West 2nd Ave | Vancouver BC | V5Y 1B3
> >> p. 604.874.8700 | f. 604.872.2106 | c. 6043461228
> >> sean.lewkiw at cis-vancouver.com
> >>
> >>
> >>
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--
Mark Elendt
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