Ross Del Duca wrote:

> I've created a model of flapping wings.  There are ribs, with bicubic
> patches forming the 'skin' between the wings.  The wings are generated with
> a macro that takes "spread" and "flap" values to determine their position -
> which can in turn be based on the clock.
> 
> What I'm trying to add now is a way to have the 'skin' stretch as if
> experiencing wind resistance.  To do that - I need someway to know the
> motion of the wing (i.e. up or down) but I'm stumped about how to do this
> since each frame is rendered individually.  Is there an easy way for me to
> track what the last frame rendered was, so that I can then determine which
> way to stretch the bicubic patch?

You're using a formula based on the clock variable to generate the
wing's position, right?

If so, then use differential calculus to derive the formula for the
wing's velocity at any given moment.

Regards,
John

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