[Sidefx-houdini-list] sdf renders as isosurface

Tom Nixon ignivomous at gmail.com
Thu Apr 4 04:41:29 EDT 2013


from SESI:

Houdini 12.5 has replaced the volume step size parameter with the
volume quality value.  For CVEX volumes, a quality of 1 corresponds to
100 steps to march through the bounding box of the procedural volume.
For voxel based volumes, a quality of 1 corresponds to 1 step per
voxel.  For voxel volumes the 0.25 default makes sense, though for
procedural volumes it may need tweaking to achieve a similar quality
since there's no voxel size to use as a basis for the default step
calculation.
	
In the future we may add a step size parameter to the CVEX volume
procedural so that the step size for quality 1 can be directly
controlled.




On Tue, Apr 2, 2013 at 3:55 PM, Tom Nixon <ignivomous at gmail.com> wrote:

> Ahh, yes, I'm getting something completely different when I render 12.1.
> It would seem that my session in 12.5 was a bit bonkers as I am now able to
> get something *similar* to what I get from 12.1. My alpha still has
> blurry edges and what looks like dropped buckets in 12.5.
>
> Seems something has changed!
>
>
> On Tue, Apr 2, 2013 at 3:34 PM, François Duchesneau <sidefx at trinix.ca>wrote:
>
>> Maybe, the version I tried is 12.1.185. In case the plastic shader hasn't
>> been upgraded properly, try rolling your own surface shader with just a
>> Lighting Model plugged into the color.
>>
>> Tom Nixon wrote:
>>
>>> Yes, I replaced the surface shader with a plastic shader.
>>>
>>> I'm wondering if something has broken in 12.5 or if I need a reboot!
>>>
>>> thx
>>>
>>>
>>> On Tue, Apr 2, 2013 at 2:39 PM, François Duchesneau <sidefx at trinix.ca
>>> >wrote:
>>>
>>>
>>>
>>>> If I open the VolumeNoiseIso example and replace the surface shader
>>>> "vopsurface1" in shopnet1/material1 by any surface shader that has a
>>>> standard illumination loop it's working. It's because the current shader
>>>> they provide is not meant to react to light but rather to show the
>>>> normals.
>>>>
>>>> You'll have to change also the code inside "vopcvex1" to include a
>>>> "Volume
>>>> Sample From File" and "Volume Gradiant From File" to read your SDF
>>>> volume.
>>>>
>>>> François
>>>>
>>>> Tom Nixon wrote:
>>>>
>>>>
>>>>
>>>>> Hi all,
>>>>>
>>>>> I've been trying in vain to get a surface render out of an sdf in
>>>>> Mantra.
>>>>>
>>>>> The VolumeNoiseIso example is */kind of/* interesting. The problem is
>>>>> that
>>>>>
>>>>> the alpha is never black. I also was unable to get the surface to
>>>>> respond
>>>>> to light in any useful way.
>>>>>
>>>>> Eventually I want to do this with VDB, but I've not even been able to
>>>>> get
>>>>> this up and running with a simple sphere and houdini volume sdf.
>>>>>
>>>>> Can anyone give me a push?
>>>>>
>>>>> Cheers,
>>>>> Tom
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>>>>> >
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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