Re: Weird Realflow problem in XSI 6

["Tim Leydecker" <BauerOink(at)gmx.de>]

> guy rabiller | 3d tachnical director (at) LaMaison

"tachnical" - what happened? You went more tactical?

But seriously, wouldn´t anyone of you guys want to forward
your findings to the Realflow/NextLimit guys?

They may have simply not realized the changes yet and
this could indeed speed things up a bit. Especially if it
came from a registered user (with impressive domain name).

I´d do it myself but I´ve actually never used the programm at all.
(Except for installing the demo and being scared away...)

Cheers

tim



----- Original Message ----- 
From: "Guy Rabiller" <guy(at)alamaison.fr>
To: <XSI(at)Softimage.COM>
Sent: Wednesday, January 10, 2007 2:50 AM
Subject: Re: Weird Realflow problem in XSI 6


> This is exactly that.
>
> It's not a mental ray issue, nor a XSI issue.
>
> The problem purely has to be handled inside the operator wich deforms the mesh.
>
> The reference time ? No need to make simple things complicated. At each frame the 
> mesh file corresponding to that frame must be loaded, that's why the scene frame 
> time has to be taken into account fisrt, and not the operator evaluation time.
>
> The operator evaluation time then is use to compute the delta between this 
> evaluation step and the frame time to, as you said, deform the mesh according to 
> this delta and the embedded motion vectors.
>
> That's it. No need to look further.
>
> --
> guy rabiller | 3d tachnical director (at) LaMaison
>
>
>
> Alan Jones a écrit :
> > Hi Matt,
> >
> > This is half the problem and half the solution.
> >
> > The actual motion vector data in itself isn't an issue at all - it's
> > right there in the realflow mesh data. XSI however doesn't have any
> > way to directly say these are the motion vectors for each vertex - so
> > in order for XSI to discover these motion vectors you need to deform
> > your mesh by them based on the time. Not a big issue in itself either.
> >
> > Where it gets complex is your mesh topology is changing, but when?
> > does it change at frame n or frame n+0.5 or some other point. To solve
> > this you need to know what time you want the mesh at, as well as a
> > base reference time (as Halfy suggested). This way the base reference
> > time is the frame for which you pull the topology, and the time you
> > want the mesh at determines where your motion vector shifts each of
> > points so that XSI will discover the motion vectors itself.
> >
> > I haven't looked into it any further than that - so I've not found
> > what the solutions are for the remaining issues (nor what all the
> > issues involved are).
> >
> > Cheers,
> >
> > Alan.
> >
> > On 1/9/07, Matt Lind <speye_21(at)hotmail.com> wrote:
> > > If I have it straight, it's up to the translator to provide motion vectors
> > > for each vertex of a mesh.  mental ray computes an interpolated motion
> > > vector at each ray intersection at render time.  In the case of realflow,
> > > the motion vectors are included (or can be) when you export the mesh from
> > > Realflow and send it to XSI.  This is how we were able to do motion blur for
> > > the milk and other liquids on 'Barnyard' using our own motion vector shader.
> > >
> > >
> > > Matt
> > >
> > > ------------------------------
> > > Matt Lind
> > > Animator / Technical Director
> > > SOFTIMAGE certified instructor:
> > >    SOFTIMAGE|3D
> > >    SOFTIMAGE|XSI
> > > Matt.Lind(at)Mantom.net
> > >
> > >
> > >
> > > Date : Tue, 9 Jan 2007
> > > To : XSI(at)Softimage.COM
> > > From : Kim Aldis
> > > Subject : RE: Weird Realflow problem in XSI 6
> > >
> > > Possibly Alan knows more about the  way motion blur works between mental ray
> > > and Realflow. It should be OpenSource though really. That way you'd get the
> > > best of everyone's knowledge, in theory at least. If they had any sense at
> > > all they'd release their code to OS. I'm sure they could do it without
> > > letting anything important out.
> > >
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