Problems with strand segment orientation

[Ahmidou Lyazidi]

Hi List
We're doing some short hairs with ICE , and getting some glitches when strands tangents are looking at the camera.
ie: the strands are turning around their tangents and loosing their consistencies as ribbons.
AFAIK the strands up vector attribute is not used by the segment shape, and the calculation of it is done by the hair geo shader
anyway I found this two MR features

Hair strand Features.

”A per-hair normal turns the hair from a flat, ray-oriented ribbon to a flat normal-oriented ribbon.”

Hair Vertex Features.

“ A per –vertex ribbon, which can change orientation, ie twist, from vertex to vertex. This can be useful for simulating grass, for example. The per-vertex radii can be used to splay individual hairs are the roots and taper them at the tips, for example for a more realistic look without excessive data.

Could those been implemented as hidden/unsupported ICE attributes?
If not, how are you guys dealing with this?

Thanks
Ahmidou Lyazidi
Director | TD | CG artist
http://vimeo.com/ahmidou/videos

[Ahmidou Lyazidi]

Here's a video showing the problem (96ko)

Ahmidou Lyazidi
Director | TD | CG artist
http://vimeo.com/ahmidou/videos

2010/11/15 Ahmidou Lyazidi <ahmid...@gmail.com>

[Robert Chapman]

yeah we are getting this here at the moment with strand hair , its as though when the strands face the camera they disapear and you are left with the roots looking like shaved 'stubble' not a good look for the ladies...   have you come across any workarounds yet?  increasing the amounts of hair and direction randomness helped a bit but its still apparent when facing directly to the camera. :/

[Alan Fregtman]

Does that happen with the Hair Geometry shader as well? Or only the
normal Hair shader?

On Wed, Nov 17, 2010 at 12:31 PM, Robert Chapman <tekan...@gmail.com> wrote:
> yeah we are getting this here at the moment with strand hair , its as though
> when the strands face the camera they disapear and you are left with the

> roots looking like shaved 'stubble' not a good look for the ladies...�� have
> you come across any workarounds yet?� increasing the amounts of hair and

> direction randomness helped a bit but its still apparent when facing
> directly to the camera. :/
>
>
> On 15 November 2010 17:27, Ahmidou Lyazidi <ahmid...@gmail.com> wrote:
>>
>> Here's a video showing the problem (96ko)
>> Ahmidou Lyazidi
>> Director | TD | CG artist
>> http://vimeo.com/ahmidou/videos
>>
>>
>>
>> 2010/11/15 Ahmidou Lyazidi <ahmid...@gmail.com>
>>>
>>> Hi List
>>> We're doing some short hairs with ICE , and getting some glitches when
>>> strands tangents are looking at the camera.
>>> ie: the strands are turning around their tangents and loosing their
>>> consistencies as ribbons.
>>> AFAIK the strands up vector attribute is not used by the segment shape,
>>> and the calculation of it is done by the hair geo shader
>>> anyway I found this two MR features
>>>
>>> Hair strand Features.
>>>

>>> �A per-hair normal turns the hair from a flat, ray-oriented ribbon to a
>>> flat normal-oriented ribbon.�
>>>
>>> Hair Vertex Features.
>>>
>>> � A per �vertex ribbon, which can change orientation, ie twist, from

[Robert Chapman]

ah , I never tried the hair Geometry shader, will give it a go, but it doesn't seem to happen with XSI hair, only with ICE strands...

On 17 November 2010 18:24, Alan Fregtman <alan.f...@gmail.com> wrote:

Does that happen with the Hair Geometry shader as well? Or only the
normal Hair shader?

On Wed, Nov 17, 2010 at 12:31 PM, Robert Chapman <tekan...@gmail.com> wrote:
> yeah we are getting this here at the moment with strand hair , its as though
> when the strands face the camera they disapear and you are left with the

> roots looking like shaved 'stubble' not a good look for the ladies...   have
> you come across any workarounds yet?  increasing the amounts of hair and

> direction randomness helped a bit but its still apparent when facing
> directly to the camera. :/
>
>
> On 15 November 2010 17:27, Ahmidou Lyazidi <ahmid...@gmail.com> wrote:
>>
>> Here's a video showing the problem (96ko)
>> Ahmidou Lyazidi
>> Director | TD | CG artist
>> http://vimeo.com/ahmidou/videos
>>
>>
>>
>> 2010/11/15 Ahmidou Lyazidi <ahmid...@gmail.com>
>>>
>>> Hi List
>>> We're doing some short hairs with ICE , and getting some glitches when
>>> strands tangents are looking at the camera.
>>> ie: the strands are turning around their tangents and loosing their
>>> consistencies as ribbons.
>>> AFAIK the strands up vector attribute is not used by the segment shape,
>>> and the calculation of it is done by the hair geo shader
>>> anyway I found this two MR features
>>>
>>> Hair strand Features.
>>>

>>> ”A per-hair normal turns the hair from a flat, ray-oriented ribbon to a

>>> flat normal-oriented ribbon.”
>>>
>>> Hair Vertex Features.
>>>

>>> “ A per –vertex ribbon, which can change orientation, ie twist, from

[Ahmidou Lyazidi]

Hi
I didn't found any workaround, and will report it to softimage.
I'm getting the same result with any shader I tryed :Muh hair, HairTK, and the factory one (this is the Geometry one, right?)
Xsi hairs have the same problem but it react differently, like if the up vector was pointing to another axis.

Ahmidou Lyazidi
Director | TD | CG artist
http://vimeo.com/ahmidou/videos

2010/11/17 Robert Chapman <tekan...@gmail.com>

[Alan Fregtman]

Now that you mention it I can't find a shader by that name in 2011. I
swear to god it was in one of the previous versions. Maybe it's been
renamed.

The default hair shader (if I'm not mistaken) draws shaded lines. The
alternate factory one I remember would render tubes of geometry --
kinda looked like tubes with a default phong. It was slower of course.

On Wed, Nov 17, 2010 at 3:14 PM, Ahmidou Lyazidi <ahmid...@gmail.com> wrote:
> Hi
> I didn't found any workaround, and will report it to softimage.
> I'm getting the same result with any shader I tryed :Muh hair, HairTK, and
> the factory one (this is the Geometry one, right?)
> Xsi hairs have the same problem but it react differently, like if the up
> vector was pointing to another axis.
>
> Ahmidou Lyazidi
> Director | TD | CG artist
> http://vimeo.com/ahmidou/videos
>
>
>
> 2010/11/17 Robert Chapman <tekan...@gmail.com>
>>
>> ah , I never tried the hair Geometry shader, will give it a go, but it
>> doesn't seem to happen with XSI hair, only with ICE strands...
>>
>> On 17 November 2010 18:24, Alan Fregtman <alan.f...@gmail.com> wrote:
>>>
>>> Does that happen with the Hair Geometry shader as well? Or only the
>>> normal Hair shader?
>>>
>>> On Wed, Nov 17, 2010 at 12:31 PM, Robert Chapman <tekan...@gmail.com>
>>> wrote:
>>> > yeah we are getting this here at the moment with strand hair , its as
>>> > though
>>> > when the strands face the camera they disapear and you are left with
>>> > the
>>> > roots looking like shaved 'stubble' not a good look for the ladies...
>>> > have

>>> > you come across any workarounds yet?� increasing the amounts of hair

>>> > and
>>> > direction randomness helped a bit but its still apparent when facing
>>> > directly to the camera. :/
>>> >
>>> >
>>> > On 15 November 2010 17:27, Ahmidou Lyazidi <ahmid...@gmail.com>
>>> > wrote:
>>> >>
>>> >> Here's a video showing the problem (96ko)
>>> >> Ahmidou Lyazidi
>>> >> Director | TD | CG artist
>>> >> http://vimeo.com/ahmidou/videos
>>> >>
>>> >>
>>> >>
>>> >> 2010/11/15 Ahmidou Lyazidi <ahmid...@gmail.com>
>>> >>>
>>> >>> Hi List
>>> >>> We're doing some short hairs with ICE , and getting some glitches
>>> >>> when
>>> >>> strands tangents are looking at the camera.
>>> >>> ie: the strands are turning around their tangents and loosing their
>>> >>> consistencies as ribbons.
>>> >>> AFAIK the strands up vector attribute is not used by the segment
>>> >>> shape,
>>> >>> and the calculation of it is done by the hair geo shader
>>> >>> anyway I found this two MR features
>>> >>>
>>> >>> Hair strand Features.
>>> >>>

>>> >>> �A per-hair normal turns the hair from a flat, ray-oriented ribbon to
>>> >>> a

>>> >>> flat normal-oriented ribbon.�
>>> >>>
>>> >>> Hair Vertex Features.
>>> >>>

>>> >>> � A per �vertex ribbon, which can change orientation, ie twist, from

[Edna Kruger]

I believe you're looking for the old the Hair Geo shader, right? it's now called the Hair Gradient Material shader.

HTH
- edna

>>> > you come across any workarounds yet?  increasing the amounts of hair

>>> > and
>>> > direction randomness helped a bit but its still apparent when facing
>>> > directly to the camera. :/
>>> >
>>> >
>>> > On 15 November 2010 17:27, Ahmidou Lyazidi <ahmid...@gmail.com>
>>> > wrote:
>>> >>
>>> >> Here's a video showing the problem (96ko)
>>> >> Ahmidou Lyazidi
>>> >> Director | TD | CG artist
>>> >> http://vimeo.com/ahmidou/videos
>>> >>
>>> >>
>>> >>
>>> >> 2010/11/15 Ahmidou Lyazidi <ahmid...@gmail.com>
>>> >>>
>>> >>> Hi List
>>> >>> We're doing some short hairs with ICE , and getting some glitches
>>> >>> when
>>> >>> strands tangents are looking at the camera.
>>> >>> ie: the strands are turning around their tangents and loosing their
>>> >>> consistencies as ribbons.
>>> >>> AFAIK the strands up vector attribute is not used by the segment
>>> >>> shape,
>>> >>> and the calculation of it is done by the hair geo shader
>>> >>> anyway I found this two MR features
>>> >>>
>>> >>> Hair strand Features.
>>> >>>

>>> >>> "A per-hair normal turns the hair from a flat, ray-oriented ribbon to
>>> >>> a

>>> >>> flat normal-oriented ribbon."
>>> >>>
>>> >>> Hair Vertex Features.
>>> >>>

>>> >>> " A per -vertex ribbon, which can change orientation, ie twist, from

[Alan Fregtman]

Gotcha. That's the one then.

Cheers, :)

-- Alan