I've just finished writing the macro which will later be used to interpolate
among the different presets for the pose of the mouth.
One might think that writing an interpolation macro from one spline to the
next is rather easy, but its not. Simply interpolating from one set of nodes
and directions to another set can get very cheesy results. My first idea was
to parse the spline and place a set of nodes along the spline, where each
node has the same distance to its respective neighbours, in effect having an
even distribution of nodes along the spline. But just interpolating the
shapes didn't work, as the positions for the mouth's corners changed from
shape to shape.
Finally, I came up with following solution: The mouth is formed with a
spline which has nodes at the corners and the middle section of upper and
lower lip. The nodes' positions are simply interpolated. But the directions
attached to them are handled slightly different for the corners. Instead of
just interpolating, I interpolate the length, but the direction is rotated
around an arbitrary axis. This simulates a crude method of muscles flexing
the corners, and gives quiet pleasant results.

In the animation that follows you'll see the mouth animate through various
poses: Wide-Smile, Sad, Content, Frightened, Wide-Smile (for looping
reasons). They don't have to be one after another, I can even interpolate
during interpolations.

For the final worm, I plan to additionally introduce displacement splines
which will each cover a quarter of the mouth, to make things like
cartoonish-shivering or "waving" of the lips possible. Though I'm not too
sure if it will be used in the short, I want to make sure that the setup
leaves near to no room for improvements (because there's nothing than can be
added once everything is there).

Comments and suggestions welcome.

Tim

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: tim.nikias (@) gmx.de



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Attachments:
Download 'mouth_tst.mpg' (149 KB)

This looks good - the only thing I would add (which should be fairly easy compared to
the splines)
is to change the interpolation method by which the expressions are morphed. Having
linear
interpolation makes it look as though the mouth is 'boucing' between expressions, so
perhaps cubic
or cosine interpolation would be better.

Alternatively, perhaps the mouth should move exponentially towards new expressions:
currentexpression = firstexpression*e^-nt + secondexpression*(1 - e^-nt)
where t is time and n controls the speed of the fade.

Perhaps also one further thing could be added - a slight and low frequency variation
of the
parameters to avoid the lips looking too fixed when they are not actually being
animated.



-Chris

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The interpolation was linear, but it is planned to be enhanced with
different methods. As you mentioned, linear looks a little cut off, and I
sure don't want to look like an amateur in my first Short Movie! :-)

As for the lips looking too fixed: I've added that displacement-mapping,
moves the lips, regardless of the underlying spline, more in- or outwards,
in relation to the normal of the lips at that point. This should make some
cartoonish effects possible, but also enable that slight movement. Maybe
I'll add some other features for that as well, depends on which ideas I come
up with and how I can implement them on the underlying structure.

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: tim.nikias (@) gmx.de


> This looks good - the only thing I would add (which should be fairly easy
compared to the splines)
> is to change the interpolation method by which the expressions are
morphed. Having linear
> interpolation makes it look as though the mouth is 'boucing' between
expressions, so perhaps cubic
> or cosine interpolation would be better.
>
> Alternatively, perhaps the mouth should move exponentially towards new
expressions:
> currentexpression = firstexpression*e^-nt + secondexpression*(1 - e^-nt)
> where t is time and n controls the speed of the fade.
>
> Perhaps also one further thing could be added - a slight and low frequency
variation of the
> parameters to avoid the lips looking too fixed when they are not actually
being animated.
>
>
>
> -Chris
>
>


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Looks really good Tim. Very smooth. Are you
going to add pouty/pursing lips (like when kissing
and various sounds like "Oh")? How about teeth?
Just curious where you're going with it...
=Bob=

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The problem with pouty/pursing lips is the connection from cylinder-head to
lips, which is why the lips are "mapped" onto the cylinder, so there'll
probably be no protruding lips. He won't be kissing anyways... Teeth? Don't
know yet. I'm working on animating it right now, and will look for teeth
later.

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: tim.nikias (@) gmx.de


> Looks really good Tim. Very smooth. Are you
> going to add pouty/pursing lips (like when kissing
> and various sounds like "Oh")? How about teeth?
> Just curious where you're going with it...
> =Bob=
>
>


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