Re: AN interesting comment.

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Elizabeth Smith (eliza++at++daisy.paradigmsim.com)
Fri, 17 Jan 1997 13:21:23 -0600

On Jan 17, 6:50pm, Angus Dorbie wrote:
> Subject: Re: AN interesting comment.
> On Jan 17, 9:51am, Rob Jenkins wrote:
>
> > http://www.math.gatech.edu/~tpan/rectangles.html
> >
>
> I know this is a Mach effect but is it the proverbial Mach banding?
> I have heard it called this before but always had an uncomfortable
> doubt.
>
> The images in the URL show this Mach effect:
>
> ____________ __________
> | /
> | /
> | |
> | |
> | /
> ______________| _________/
>
> actual intensity perceived intensity
>
>
> And I thought Mach banding was:
> __
> ____________ / \_________
> / /
> / /
> / /
> / /
> / /
> / /
> actual intensity perceived intensity
>
> Graph axes guide:
>
> (intensity)
> ^
> |
> |
> |
> -------> (space)
>
> Hence a percieved intensity band where none exists, often seen in
> graphics when intensity gets clamped to a maximum value.
>
> Any takers for this Fridays pub trivia question? I think Foley van Damn
> is where I remember these graphs from but my copy is at home.

Figure 16.17 of F&VD c1990 confirms the correctness of your graphs.

Also, in the same book, see section 21.5 "Problems Peculiar
to Animation" for a discussion of the "double framing", called
"animating by twos" on page 1080. It mentions only the
jerkiness of animations so generated.

> Cheers,
> Angus.
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>-- End of excerpt from Angus Dorbie

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