I am designing a character, mainly with blobs. I want to add eyelashes but I
have trouble determining where to put the lashes. I have a blob-sphere for
the head with a blob-sphere for the eyelids. The eye opening is a squashed
negative-strength blob-cylinder which I scale according to how far open the
eyes are. The eyelashes need to be at the edge where the eyelid and
negative blob-cylinder meets. Does anyone know how I can determine this
please?

Regards
Nekar Xenos

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"Nekar Xenos" <go_### [at] yahoocom> wrote in message 
news:web.434d698a93356c48602b380@news.povray.org...
>I am designing a character, mainly with blobs. I want to add eyelashes but 
>I
> have trouble determining where to put the lashes. I have a blob-sphere for
> the head with a blob-sphere for the eyelids. The eye opening is a squashed
> negative-strength blob-cylinder which I scale according to how far open 
> the
> eyes are. The eyelashes need to be at the edge where the eyelid and
> negative blob-cylinder meets. Does anyone know how I can determine this
> please?
>
> Regards
> Nekar Xenos
>

Hi Nekar,

I don't know of a simple way, though someone with a better feel for blobs 
may be able to tell you how to calculate where the boundary comes.

You're right that it can be done with Trace. There's probably loads of ways 
to approach it, but I would suggest identifying a series of start points 
that would form an arc a short distance outside an eyelid as you look down 
from above.
If you select a height that aligns with your negative strength cylinder, 
then it should be level with the opening. You could then send out a series 
of traces from each start point, scanning vertically to find the two 
intersection points closest to that start point (one above the horizontal, 
one  below).

I would then store the upper eye line positions in an array and the normals 
in a second array and use a loop to position eye lashes uniformly along the 
line. I've got SDL to do this last little bit (the easy bit) if you're 
interested.

Regards,
Chris B.

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> Hi Nekar,
>
> I don't know of a simple way, though someone with a better feel for blobs
> may be able to tell you how to calculate where the boundary comes.
>
> You're right that it can be done with Trace. There's probably loads of ways
> to approach it, but I would suggest identifying a series of start points
> that would form an arc a short distance outside an eyelid as you look down
> from above.
> If you select a height that aligns with your negative strength cylinder,
> then it should be level with the opening. You could then send out a series
> of traces from each start point, scanning vertically to find the two
> intersection points closest to that start point (one above the horizontal,
> one  below).
>
> I would then store the upper eye line positions in an array and the normals
> in a second array and use a loop to position eye lashes uniformly along the
> line. I've got SDL to do this last little bit (the easy bit) if you're
> interested.
>
> Regards,
> Chris B.

Thanks, this is roughly along the lines that I tried, but it looks like what
I really need here is a mathematical formula to determine where the
positive and negative blobs meet.

Regards,
Nekar Xenos

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First of all you always have the option of being a non-purist and just make
a 

union{
        your_blob_object
        difference{sphere{}
                   slightly smaller sphere{}
                   cylinder{}
                }
        and then rotate this differenced object as you would an eyelid.

Secondly, you could make the object that cuts the eye-hole rotate itself,
then you could just give eyelashes the same transform as the eyelid.


                

Nekar Xenos wrote:

> I am designing a character, mainly with blobs. I want to add eyelashes but
> I have trouble determining where to put the lashes.

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