[Sidefx-houdini-list] Shading artifact when really close to surface

Andrew D Lyons tstexture at gmail.com
Wed Oct 21 14:35:53 EDT 2009


Internally Houdini still uses floats (real) instead of doubles in many
places - so I wouldn't think so.

Doesn't putting big transforms in /obj nodes instead of transform SOPs
improve/ remove certain distance related precision errors with certain
renderers? For packages that flatten transforms, and don't feed
seperate local and object space co-ordinates into the scene
description (ifd/rib etc) precision errors like what Ivan is talking
about can be a real problem, but I think Houdini gets around it if you
use the obj node for your big transforms. Not sure if that wopks for
the viewport though. OpenGL supports hierarchical transforms - so I'd
hope so.

Cheers


2009/10/21  <craigleehoffman at aol.com>:
>
>
>
>  Ivan,
>
> Do any of the precision problems improve if you move from 32 bit to 64 bit Houdini?
>
> Thanks,
> Craig
>
>
>
> -----Original Message-----
> From: Ivan DeWolf <ivan at martian-labs.com>
> To: sidefx-houdini-list at sidefx.com; Francois Duchesneau <sidefx at trinix.ca>
> Sent: Wed, Oct 21, 2009 11:19 am
> Subject: Re: [Sidefx-houdini-list] Shading artifact when really close to surface
>
>
>
>
>
>
>
>
>
>
>
> another problem you seem to have is floating point error.
> Your are a couple of meters above sea level, but the center of your
> geometry is at the center of the earth, thousands of kilometers away.
> If you move your scene closer to the centroid, you will have fewer
> issues.
>
>
> To understand a bit about floating point error, put down a"box" sop
> (in an empty scene) and hit space-g and tumble it. Nice and happy.
> Now set it's X center to 1000000 and hit space-g
> tumble and its all jumpy... and one more zero and tumble and it
> doesn't even look like a cube.....
>
> in a computer, if you a really far from the origin and moving small
> distances, you get floating point errors.
>
> The difference betweeen 1000000.036 and 1000000.037 is very different
> from .036 and .037 in the computer....
>
>
>
>
> _______________________________________________________
> Perfection is achieved when nothing else can be removed
> -Yvon Chouinard
>
> ----------------------------------------------------------------
> This message was sent using IMP, the Internet Messaging Program.
> _______________________________________________
> Sidefx-houdini-list mailing list
> Sidefx-houdini-list at sidefx.com
> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>
>
>
>
>
> _______________________________________________
> Sidefx-houdini-list mailing list
> Sidefx-houdini-list at sidefx.com
> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>



-- 
=======================================
Andrew D Lyons | Digital Artist | http://www.tstex.com
=======================================



More information about the Sidefx-houdini-list mailing list