RE: XSI hair and Random Generation

[Fabrice Altman]

There is something similar happening if you turn render Hair Generation > 
Render quality to Low (fastest), on the main PPG.

From: softimage-boun...@listproc.autodesk.com 
[mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Tim Crowson
Sent: 14 July 2014 14:23
To: softimage@listproc.autodesk.com
Subject: XSI hair and Random Generation

Is there something about XSI's standard hair primitives (not ICE) that causes 
the hairs to be generated slightly differently each time a scene is opened? 
We're rendering with Redshift, but I'm thinking we saw something like this a 
few years ago with Mental Ray as well. Basically, on the farm, some machines 
will render their frame ranges with slightly different hair than any other 
machine. The only solution seems to be to render all the hair on a single 
machine, and to do so in a way that keeps the scene open (so in the case of 
Royal Render for instance, set the sequence maximum to be the full range you 
need).

The rendered hair isn't 'bad' per se, it's just 'different' from surrounding 
frame ranges. The simplest description is that each machine seems to want to 
render the hair slightly differently. And I really wonder if it's not some bug 
with XSI hair.
--



Tim Crowson
Lead CG Artist

Magnetic Dreams, Inc.
2525 Lebanon Pike, Bldg C, Suite 101, Nashville, TN 37214
Ph  615.885.6801 | Fax  615.889.4768 | 
www.magneticdreams.com<http://www.magneticdreams.com>
tim.crow...@magneticdreams.com<mailto:tim.crow...@magneticdreams.com>

Re: XSI hair and Random Generation

[Tim Crowson]

Thanks, I don't think it's an issue with textures not being found 
though. Also the problem can even happen on a single machine, if the 
scene is closed and re-opened.

Computers, man! Blargh!

-Tim

On 7/14/2014 10:02 AM, Stefan Kubicek wrote:
I rendered hair from the same scene across multiple machines and never 
ran into this. That was with 3delight, though I doubt there is a 
dependency on the actual renderer as XSI is responsible for delivering 
the full hair description to the renderer.
However, what I did not use was clumping (Hair Multiplicity), in case 
you use that you might want to try to turn it off and render a few 
frames on all machines and see if that "fixes" the problem. Is the 
problem persistent on just those few machines, or does it wander 
across machines?
If it's always the same machines,  maybe you are using some sort of 
cut map (or other map influencing hair geometry) and some machines 
can't find that texture, hence rendering the hair slightly different 
on those machines that can't find it?




Is there something about XSI's standard hair primitives (not ICE)
that causes the hairs to be generated /slightly differently/ /each
time a scene is opened/? We're rendering with Redshift, but I'm
thinking we saw something like this a few years ago with Mental
Ray as well. Basically, on the farm, some machines will render
their frame ranges with slightly different hair than any other
machine. The only solution seems to be to render all the hair on a
single machine, and to do so in a way that keeps the scene open
(so in the case of Royal Render for instance, set the sequence
maximum to be the full range you need).

The rendered hair isn't 'bad' per se, it's just 'different' from
surrounding frame ranges. The simplest description is that each
machine seems to want to render the hair slightly differently. And
I really wonder if it's not some bug with XSI hair.
-- 
Signature

Re: XSI hair and Random Generation

[Stefan Kubicek]

I rendered hair from the same scene across multiple machines and never ran into 
this. That was with 3delight, though I doubt there is a dependency on the 
actual renderer as XSI is responsible for delivering the full hair description 
to the renderer.
However, what I did not use was clumping (Hair Multiplicity), in case you use that you 
might want to try to turn it off and render a few frames on all machines and see if that 
"fixes" the problem. Is the problem persistent on just those few machines, or 
does it wander across machines?
If it's always the same machines,  maybe you are using some sort of cut map (or 
other map influencing hair geometry) and some machines can't find that texture, 
hence rendering the hair slightly different on those machines that can't find 
it?




Is there something about XSI's standard hair primitives (not ICE) that causes the hairs to 
be generated slightly differently each time a scene is >opened? We're rendering with 
Redshift, but I'm thinking we saw something like this a few years ago with Mental Ray as 
well. Basically, on the >farm, some machines will render their frame ranges with 
slightly different hair than any other machine. The only solution seems to be to render all 
>the hair on a single machine, and to do so in a way that keeps the scene open (so in 
the case of Royal Render for instance, set the sequence >maximum to be the full range 
you need).

The rendered hair isn't 'bad' per se, it's just 'different' from surrounding frame 
ranges. The simplest description is that each machine seems to want >to render 
the hair slightly differently. And I really wonder if it's not some bug with XSI 
hair.
--

Tim Crowson
Lead CG Artist

Magnetic Dreams, Inc.
2525 Lebanon Pike, Bldg C, Suite 101, Nashville, TN 37214
Ph  615.885.6801 | Fax  615.889.4768 | www.magneticdreams.com
tim.crow...@magneticdreams.com






--

-
   Stefan Kubicek ste...@keyvis.at
-
  Alfred Feierfeilstraße 3
A-2380 Perchtoldsdorf bei Wien
 Phone: +43 (0) 699 12614231
   www.keyvis.at
 This email and its attachments are
confidential and for the recipient only

Re: XSI hair and Random Generation

[Tim Crowson]

Thanks, that's interesting. In our case though, I'm talking about a 
single shot, which means all machines will load the exact same scene 
file at render time. I think RR starts by opening the scene, moving the 
playhead (internally of course since it's xsibatch) to whatever the 
scene's in-point is, then moving the playhead to the frame that's 
supposed to be rendered. And up until that last move, everything should 
be the same from machine to machine.




On 7/14/2014 9:26 AM, Jonah Friedman wrote:
I believe it has to do with what frame the scene was loaded on. IE, 
the hair is generated from the mesh's position when the scene loads, 
then the scene advances to the right frame, and it uses the 
distribution from where it loaded.


This is partially superstition, but IIRC those were the rules, and 
these issue occur when you render on the farm using scenes left on 
different frames.



On Mon, Jul 14, 2014 at 9:45 AM, Ed Manning > wrote:


IIR, this is indeed an old issue that I remember seeing in MR.  I
think it's not a bug per se, but a limitation of how XSI hair
primitives are internally dependent on previous frames' data. I
don't think there was ever any workaround other than doing all the
hair consecutively on one machine. Maybe some way of caching the
hair?




--
Signature

Re: XSI hair and Random Generation

[Jonah Friedman]

I believe it has to do with what frame the scene was loaded on. IE, the
hair is generated from the mesh's position when the scene loads, then the
scene advances to the right frame, and it uses the distribution from where
it loaded.

This is partially superstition, but IIRC those were the rules, and these
issue occur when you render on the farm using scenes left on different
frames.


On Mon, Jul 14, 2014 at 9:45 AM, Ed Manning  wrote:

> IIR, this is indeed an old issue that I remember seeing in MR.  I think
> it's not a bug per se, but a limitation of how XSI hair primitives are
> internally dependent on previous frames' data. I don't think there was ever
> any workaround other than doing all the hair consecutively on one machine.
> Maybe some way of caching the hair?
>

Re: XSI hair and Random Generation

[Ed Manning]

IIR, this is indeed an old issue that I remember seeing in MR.  I think
it's not a bug per se, but a limitation of how XSI hair primitives are
internally dependent on previous frames' data. I don't think there was ever
any workaround other than doing all the hair consecutively on one machine.
Maybe some way of caching the hair?

RE: XSI hair and Random Generation

[gareth bell]

I half recall coming across something like this before. You need to lock it 
down, be it freeze it or cache it or something I think


Date: Mon, 14 Jul 2014 08:23:04 -0500
From: tim.crow...@magneticdreams.com
To: softimage@listproc.autodesk.com
Subject: XSI hair and Random Generation


  


  
  
Is there something about XSI's standard hair primitives (not ICE)
that causes the hairs to be generated slightly differently each
  time a scene is opened? We're rendering with Redshift, but I'm
thinking we saw something like this a few years ago with Mental Ray
as well. Basically, on the farm, some machines will render their
frame ranges with slightly different hair than any other machine.
The only solution seems to be to render all the hair on a single
machine, and to do so in a way that keeps the scene open (so in the
case of Royal Render for instance, set the sequence maximum to be
the full range you need).



The rendered hair isn't 'bad' per se, it's just 'different' from
surrounding frame ranges. The simplest description is that each
machine seems to want to render the hair slightly differently. And I
really wonder if it's not some bug with XSI hair.

-- 

  Signature
  
   

  Tim Crowson

  Lead
CG Artist

  Magnetic Dreams, Inc.

  2525
  Lebanon Pike, Bldg C, Suite 101, Nashville, TN 37214

  Ph  615.885.6801 | Fax  615.889.4768 |
  www.magneticdreams.com

  tim.crow...@magneticdreams.com

   

  

XSI hair and Random Generation

[Tim Crowson]

Is there something about XSI's standard hair primitives (not ICE) that 
causes the hairs to be generated /slightly differently/ /each time a 
scene is opened/? We're rendering with Redshift, but I'm thinking we saw 
something like this a few years ago with Mental Ray as well. Basically, 
on the farm, some machines will render their frame ranges with slightly 
different hair than any other machine. The only solution seems to be to 
render all the hair on a single machine, and to do so in a way that 
keeps the scene open (so in the case of Royal Render for instance, set 
the sequence maximum to be the full range you need).


The rendered hair isn't 'bad' per se, it's just 'different' from 
surrounding frame ranges. The simplest description is that each machine 
seems to want to render the hair slightly differently. And I really 
wonder if it's not some bug with XSI hair.

--
Signature

*Tim Crowson
*/Lead CG Artist/

*Magnetic Dreams, Inc.
*2525 Lebanon Pike, Bldg C, Suite 101, Nashville, TN 37214
*Ph*  615.885.6801 | *Fax*  615.889.4768 | www.magneticdreams.com
tim.crow...@magneticdreams.com