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Date: Tue, 20 Jun 95 07:41 CDT
From: johnc@mcs.com (John Crookshank)
To: lightwave@webcom.com (lightwave)
Subject: Rendering Backwards
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On 19-Jun-95 00:23:58, Ernie Wright (erniew@access.digex.net) E-Mailed:
> On rendering the first half of a periodic anim and appending a reversed
> copy to finish it, Eric Chard wrote:
>> Just to make sure, I just did it again, and no, for whatever reason
>> the field flip does not solve this particular problem. Matter of fact
>> (henceforth, "MOF") it makes it look worse.
>>
>> Time for Ernie to step in and tell us why! :^)
> Like I have any idea.
> Okay, I have -one-. It's specifically a field rendering problem, and
> not something that flipping fields will solve. This is a little hard
> to diagram in ASCII-Vision, but consider the following:
> (1 2) (3 4) (5 6)
> Each pair of numbers represents a frame with two fields. The fields
> are 1/60 of a second apart, so whatever it is we're counting with those
> numbers, it advances by one per field and two per frame. (Buying this
> so far?) If you're ready to reverse at this point, what's the next
> frame?
> If we use (3 4) we get a jump from 6 to 3:
> ... (5 6) (3 4) ...
> If we reverse fields and use (4 3), we get a jump from 6 to 4:
> ... (5 6) (4 3) ...
> See? What we really want is
> ... (5 6) (5 4) ...
> and I'm not sure how to do that.
Well, if you were to "flip fields", you would render:
(2 1) (4 3) (6 5)
Then if you were to record this backwards, you would get:
(6 5) (4 3) (2 1)
Isn't this exactly what you would want for a backwards animation?