[Sidefx-houdini-list] Swimming noise displacement

Floyd Gillis floyd at afcg.com
Sat Jul 7 18:34:14 EDT 2012


Dan & Francois,

Thank you for your help.

- Did not see a grey netbox near the bottom of the mantraSurface network.
- Geometry is stationary, simple polys with a locked SOP as 2nd input to 
the rest SOP.
- Sample lock was disabled.

There might me something else I'm missing or doing wrong... will be back 
in the office later today to do more testing.  If I still can't get it 
working I'll send more details or a simple hip file.

Cheers,

Floyd


On 7/7/2012 7:24 PM, Dan Wills wrote:
> H12.0.634 on linux here, and sorry I'm probably not much help because 
> it seems to work fine for me.
>
> It looks like mantraSurface is set up to do the right thing with the 
> built-in noise displacement. It contains a turbnoise node, inside the 
> grey netbox near the bottom of the network (as Floyd suggests), 
> labeled "Displacement". The noise is looked up using a 'Rest Position' 
> node, which is (by default at least) set to 'Object Space', so it 
> shouldn't be affected by camera movement, unless there is something 
> special about your geometry. Maybe you do have a 'rest' attribute that 
> is moving?
>
> Is the geometry definitely locked to its local space? (in other words, 
> if it is moving then it is because of Object level transformation, not 
> SOPs level deformation)
>
> One thing I wondered was whether the swimming you are perceiving might 
> be to do with the mantra setting 'Sample Lock'. Is the swimming 
> perhaps only in the very highest frequencies of detail (ie per-pixel 
> level)? If so, you might like to do a test with 'Sample Lock' disabled 
> and see if what you thought was noise was actually a locked sampling 
> pattern.
>
> Sorry I'm not much help, but you might need to provide a little more 
> detail about what's going wrong :).
> Dan
>
> On Sat, Jul 7, 2012 at 1:56 PM, Floyd Gillis <floyd at afcg.com 
> <mailto:floyd at afcg.com>> wrote:
>
>     Hi Francois,
>
>     Thanks for the suggestion... unfortunately I'm not too familiar
>     with VOP-land and would need much more detailed instructions on
>     making the changes.
>
>     Cheers,
>
>     Floyd
>
>
>
>     On 07/07/2012 1:00 PM, François Duchesneau wrote:
>
>         Have a look inside the shader and find what drives the
>         displacement noise, below in a gray network box if I'm not
>         wrong. From there you can always use P and transform it to
>         world space with a Transform Vop and plug that into the P plug
>         of the noise. But I'm surprised that the rest doesn't work, I
>         would think that this shader has that built-in.
>
>         François
>
>         Floyd Gillis wrote:
>
>             H12.0.626 on linux
>
>             Have enabled "Noise", (without "True Displacements"),
>             under the Displacement tab of a "Mantra Surface Shader".
>
>             Also have an animated Y offset to give a moving ripple
>             effect through the geometry.
>
>             Everything works fine until I move the camera... which
>             causes the noise to swim through the geometry.
>
>             Adding a rest SOP doesn't seem to have any effect.
>
>             Any other suggestions on how to keep the noise fixed to
>             the geometry when the camera moves?
>
>             Thanks
>
>
>
>
>
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