[Sidefx-houdini-list] Recursive cookie in many axis

Andrew D Lyons tstexture at gmail.com
Wed Aug 29 12:53:17 EDT 2007


Hmm, now there's food for thought.

Thanks!


On 29/08/2007, Ben Schrijvers <ben.schrijvers at guerrilla-games.com> wrote:
> Well there's different reasons not elaborate to much.
> The only thing that's new in H9 is that you can turn a bunch of polys
> into a volume primitive.
> That primitive can then be sampled in a vex i3d shader with a new vex
> function.
> So the i3d shader knowns what's inside or outside the volume which is
> exactly what replaces the cookie sop.
> I'm using a simple 3D noise in the i3d shader to offset P while I'm
> checking if I'm in or outside a cell.
> This results in a distorted cell sides.
> But uhm.. the real tricky bit is where I need to stitch up those inner
> cells back to the original outer polygons, remaining their uv's and keep
> the cracks invisible. And last but not least keep a low poly count...
>
> cheers,
> benS
>
> Andrew D Lyons wrote:
> > Volume primitives and noise are something I've been meaning to look
> > at. What are you using for voxel noise shaders? If possible, could you
> > please elaborate on your implementation?
> >
> > Thanks!
> >
> >
> > On 28/08/07, Ben Schrijvers <ben.schrijvers at guerrilla-games.com> wrote:
> >
> >> I've done some breakup tools before using cookie but it was just too
> >> unstable.
> >> As I'm now creating geometry for games the cookie has another bad side
> >> effect in that it creates unwanted/unnessecary polygons because of the
> >> nessecary pre-triangulation.
> >>
> >> At the moment I'm testing H9 and the new volume primitive type is saving
> >> the day.
> >> That combined with voxel noise shaders and I'm getting full 3D voronoi
> >> breakup.
> >>
> >> cheers,
> >> benS
> >>
> >>
> >> Andrew D Lyons wrote:
> >>
> >>> The Volume idea sounds nice. It would be of immense value to have some
> >>> kind of a 3D voronoi break up routine in Houdini that worked like
> >>> this.
> >>>
> >>> http://www.cs.cornell.edu/Info/People/chew/Delaunay.html
> >>>
> >>> I made a Houdini procedural break up tool that kind of what you wanted
> >>> at a previous place of employ. It used the "Foreach" Sop system that
> >>> was on odforce, but you could now use the For SOP in Houdini 9. It
> >>> used the cookie sop, and procedurally generated cylindrical cutters.
> >>> There was a bit of checking for bad topology and other undesirable
> >>> outcomes which would occasionally occur in the process of 100
> >>> iterations with a cookie sop and a random cutter. From memory, the
> >>> basic algorithm was:
> >>>
> >>> 1./ Use input bounds to build cutter to suitable scale.
> >>> 2./ Add random orientation, position and point displacement to cutter points.
> >>> 3./ Make cut.
> >>> 4./ Check connectivity for only 2 objects.
> >>> 5./ Measure surface area of two objects
> >>> 6./ Feed all objects back into 1 and cut the biggest object in the next pass.
> >>>
> >>> It worked OK with some hand holding, but it wasn't really that elegant
> >>> a solution in comparison to the voronoi type solutions that could be
> >>> done.
> >>>
> >>> http://compgeom.cs.uiuc.edu/~jeffe/compgeom/demos.html
> >>>
> >>> I'd definitely like to add weight to the various RFEs that are open
> >>> for a break-up tool of this sort. It would be sooo handy with DOPs...
> >>>
> >>> Cheers
> >>>
> >>>
> >>> On 26/08/07, sidefx at trinix.ca <sidefx at trinix.ca> wrote:
> >>>
> >>>
> >>>> I'm hesitating about using a recursive mechanism to break objects apart
> >>>> for a volume object that has to be cut in many axis, not only in the same
> >>>> plane like a window. I tried it but the result wasn't an artistically
> >>>> viable solution.
> >>>>
> >>>> My conclusion is, if it's for background chunk objects then it can be
> >>>> usefull. If it's for "hero chunks" or even for mid distance chunks then
> >>>> you need to decide where the cutters are.
> >>>>
> >>>> I wonder what you think about it and does anyone have an idea how we could
> >>>> cut  procedurally an object such as a sphere to make it look as if made of
> >>>> stone with nice turbulence deformation. It would be even better if we
> >>>> could provide the chunk's density by setting an attribute on a point cloud
> >>>> or volume primitive in world space inside the object but it's probably an
> >>>> utopian idea.
> >>>>
> >>>> Thanks for feedbacks
> >>>>
> >>>> François
> >>>> _______________________________________________
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> >>>> Sidefx-houdini-list at sidefx.com
> >>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >>>>
> >>>>
> >>>>
> >>>
> >>>
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> >>
> >
> >
> >
>
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Andrew D Lyons | Digital Artist | http://www.tstex.com
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