[Sidefx-houdini-list] overlapping point instance volume density pop

Dan Wills gdanzo at gmail.com
Wed May 31 07:41:32 EDT 2017


G'day Tom,

I've inferred that you're rendering in Mantra (afaik the only thing working
with Packed Disk Primitive (though, I could easily be wrong about that))..
and how are your VDBs being shaded?

I've also seen rendering issues with multiple VDBs overlapping. Not
entirely sure that what I saw matches exactly with the problems you're
seeing Tom, but if you /are/ rendering VDB volumes, perhaps you could try
converting to Houdini Volume Primitives instead? (VDB Convert Sop).

I guess merging them all into one VDB is not an option? VDB *is* quite good
at this!
If you were *really* instancing-it-up before (thousands of copies of 5
things or something), then.. that's probably not a good option.
But, if there's only a few and you can just merge 'em all into one VDB..
then that nicely works around rendering overlapping VDBs any more (as long
as its then the only one in the render), and still renders using a VDB
file! (no format-change to bgeo) ;D.

Best of luck!
Dan

On Tue, May 30, 2017 at 6:15 PM, Olivier Jeannel <facialdeluxe at gmail.com>
wrote:

> I had some vdb problems when in vop I setted the density going to values
> greater than 1.
>
>
> On Tuesday, May 30, 2017, Tom Nixon <ignivomous at gmail.com> wrote:
>
> > Hi Francois,
> >
> > I'm afraid I'm seeing something more than just a sum of two densities.
> The
> > issue is that there is a visible change in the form of a "pop" between
> two
> > density levels. This is not apparent when isolating the individual volume
> > instances.
> >
> > This is to say a region of the render appears to drop or increase in
> > density from one frame to the next. When each instance is rendered alone,
> > the pop does not happen.
> >
> > Unfortunately, rendering each volume individually is not a viable
> solution
> > to my problem.
> >
> > Thanks
> >
> > On Mon, May 29, 2017 at 6:58 PM, François Duchesneau <houdini at trinix.ca
> > <javascript:;>>
> > wrote:
> >
> > > Hi Tom,
> > >
> > > It's normal to have an increase of density when two volumes overlap.
> You
> > > can reproduce it by rendering two volume sphere overlapping a little
> bit.
> > > Are you referring to something else?
> > >
> > > Francois
> > >
> > >
> > > On 05/29/2017 07:04 PM, Tom Nixon wrote:
> > >
> > >> Hey everyone,
> > >>
> > >> I'm getting a result in my renders that I'm don't fully understand
> yet.
> > I
> > >> hope one or some of you have come across this and can shed some light
> on
> > >> it.
> > >>
> > >> I have a number of volumes that are being instanced as packed disk
> > >> primitives in my renders. The density appears to pop up and down a
> > couple
> > >> times through the frame range.
> > >>
> > >> When I isolate each volume and render it, I am unable to see the same
> > pop
> > >> in the renders.
> > >>
> > >> It appears that the pop is a result of the overlapping volumes, as
> when
> > I
> > >> offset the points to reduce the overlapping and render them together,
> > the
> > >> pop appears to disappear.
> > >>
> > >> If anyone has any experience with this, I'd appreciate your input!
> > >>
> > >> Thanks,
> > >> Tom
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> > >>
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