[Sidefx-houdini-list] Swimming noise displacement

Floyd Gillis floyd at afcg.com
Sun Jul 8 01:20:00 EDT 2012


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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