[Sidefx-houdini-list] Swimming noise displacement

Floyd Gillis floyd at afcg.com
Sun Jul 8 23:06:29 EDT 2012


Just another follow-up.

Went to update all the other mantraSurface shader nodes in my hip file 
and discovered that only two of dozens were "older versions".

Ends up these two were not "older versions", but "Glass" shaders pulled 
in from the Material Palette.

So, be aware the "Glass" shader has this problem with swimming noise 
displacements.

Floyd


On 08/07/2012 2:20 PM, Floyd Gillis wrote:
> Found the problem.
>
> The reason the displacement was swimming and I couldn't find the grey 
> netbox with the "Displacement" nodes is because I had an older version 
> of the mantraSurface shader in my hip file. (Probably from using a hip 
> file built with an earlier version of h12)
>
> Now that I've loaded up a clean mantraSurface shader the displacement 
> sticks, (even without a rest sop), and I can see the netbox with the 
> Displacement nodes.
>
> Time to update all the other old mantraSurface shaders in my hip 
> file.  Ugh!
>
> Thanks for your help.
>
> Floyd
>
>
> On 08/07/2012 8:49 AM, Christian Waite wrote:
>> If its swimming when the camera is moving its because the p position is
>> taken from the wrong space. In shaders it's using the camera point
>> position, you need to lay down a transform node (in the shader) and 
>> convert
>> it from current space to work space before going into the p input of the
>> noise shop...
>>
>> C
>>
>> On Saturday, July 7, 2012, Floyd Gillis wrote:
>>
>>> 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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