[Sidefx-houdini-list] sdf renders as isosurface

Olex P hoknamahn at gmail.com
Thu Apr 4 06:08:23 EDT 2013


> For voxel volumes the 0.25 default makes sense

Sounds a bit like astrology to me.


On Thu, Apr 4, 2013 at 9:41 AM, Tom Nixon <ignivomous at gmail.com> wrote:

> 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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