Ptex fur?

[ottermike]

Can ptex techniques be useful for generating/styling fur onto geometry?

[brentb]

On May 14, 10:59 am, ottermike <notanym...@gmail.com> wrote:
> Can ptex techniques be useful for generating/styling fur onto geometry?

We use Ptex maps to control hair/fur density, grooming, shading etc.,
and our hair/fur procedural geom system, XGen (http://portal.acm.org/
citation.cfm?id=965411), was the first software at Disney to use
Ptex. The main benefits were the simplicity of the mapping, and the
Ptex api provided a convenient and efficient cache.

[brentb]

On May 14, 10:59 am, ottermike <notanym...@gmail.com> wrote:

> Can ptex techniques be useful for generating/styling fur onto geometry?

It just occurred to me that there's another possible dimension to your
question. If your talking about controlling / shading hair along it's
length, we use Ptex for this as well, though it's not really a "per-
face texture" at that point. We sometimes use textures that map along
the length of the primitive and the Ptex format can be used to store a
large number of texture variants in a single file where the Ptex face-
id is used as a variant-id.

In a similar way we have also used Ptex as a procedural geom baking
format where we combined object-id, primitive-id, and primitive-face-
id to produce a unique mapping into the Ptex file, storing the offset
tables as Ptex meta data. For instance, we've baked PRT coefficients
on trees this way. This has advantages in size and accuracy (and
probably speed) to a comparable density point cloud.

[ottermike]

Thanks. Did you implement this in Maya, or with Disney's other
pipeline tools? I'm wanting to try and make a Ptex fur simulation in
Maya since that's all I've been taught to use. Do I have to worry
about how the fur is generated on a geometry with a ptex node attached
to it? Or would it generally work the same as Maya's fur system except
that the fur generated is not dependent on the geometry at all, just
on it's Ptex information? Would that make it more difficult to make
tools in Maya to groom/style the Ptex-generated fur?

[brentb]

On May 16, 8:53 am, ottermike <notanym...@gmail.com> wrote:
> Thanks. Did you implement this in Maya, or with Disney's other
> pipeline tools? I'm wanting to try and make a Ptex fur simulation in
> Maya since that's all I've been taught to use. Do I have to worry
> about how the fur is generated on a geometry with a ptex node attached
> to it? Or would it generally work the same as Maya's fur system except
> that the fur generated is not dependent on the geometry at all, just
> on it's Ptex information? Would that make it more difficult to make
> tools in Maya to groom/style the Ptex-generated fur?

Can you be more specific about what you are trying to do? Are you
asking how to write a fur system in Maya using Ptex? Or are you
asking how to use Maya's fur system with Ptex? In either case, these
sound more like Maya questions than Ptex questions.

[ottermike]

Sorry, I meant both, I guess. If you can drive all of Maya's fur
attributes with ptex, then would it even be necessary to program
another fur system?