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EnigmA Amiga Run 1998 July
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EnigmA AMIGA RUN 29 (1998)(G.R. Edizioni)(IT)[!][issue 1998-07 & 08].iso
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size_morphing
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1998-03-01
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Date: Tue, 23 Dec 1997 13:53:06 +0000
From: Nancy Jacobs <illusory@MIP.NET>
Subject: [IML] QUEST: maddening irrational animation problem
Hi,
Can someone figure this one out?
I have an animation that contains two identical disks with holes in
the center. All the disks do is get larger over about 12 frames,
simulating rays emanating from an object. Each disk is set to appear
at a certain size (one size frame is set) and morph to the next size
(size bar set over the next 10 or so frames). Then, the actor
disappears for several frames, then reappears with the same
configuration (done in the action editor with copy and paste). Should
work, right?
Well, it works fine in the first sequence for each disk. Problem is,
in each sequence after that, the disk gets SMALLER (way smaller than
the initial setting for it) before it gets larger again. There is
nothing happening anywhere to account for this. Other objects in the
scene are unaffected. I have tried this animation set up a couple of
very different ways, and this happens every time!
A CLUE: The small size that the disk goes down to just happens to be
about the size of the original disk object before I scaled it up in
the stage editor. However, when I scaled it up (and rotated and
positioned it), I did hit the size, position, and alignment bars,
and the correct information is right there when I go to the action
dialog.
I was up all night trying to straighten this out and I'm going
nuts....is this some kind of bug?
Any help will be very appreciated.
----------------------------------
Date: Tue, 23 Dec 1997 12:27:19 -0800
From: Clae & Deborah Tanett <cd@ACCUTEK.COM>
Hi Nancy
Clae here
In the Action editor check your spline interpolation and Discontinuous Knots
on the size bar (if they're checked uncheck them and see if that helps - try
it in the others if you need or want to - align, posn, Actor). With Imagine
for Amiga (IFA) you would go to the Action Editor; BUT with Imagine for
Windows (IFW) you go to menu: Editor/Action Dialog and double click on the
the object's size bar (I D/L Impulse's IFW demo awhile ago so I could see
the difference between the two platforms - I use IFA). Hope this helps. If
you're using IFD (Imagine for Dos i.e. Windows 3.1 +) good luck on finding
the Action stuff :).
----------------------------------
Date: Wed, 24 Dec 1997 06:47:15 -0500
From: gregory denby <gdenby@TWAIN.HELIOS.ND.EDU>
Nancy,
Good to see Clae had the tip that solved your problem.
>Now if I only understood why Spline interpolation would
>arbitrarily make my object way smaller than it was ever supposed to
>be in the animation, I could rest comfortably...
O.K. get comfortable.
Spline interpolation effects all sorts of parameters in a way that I
can only think of as counter intuitive. For instance, if something
is at rest, and begins moving, as we all know, turning it to the side
requires both a push in the new direction, and another to stop the
motion in the first direction. If we were spline interpolated, however,
before we got up from our chair, and started running, we would be pushed
down into our chair by the future force of our getting up! Spline interpolation
adds in the inertia from events which are yet to happen to any vector
it is influencing. So part of the "force" which you apply to a disk
to make it bigger will be backwards applied to the disks original size,
making it shrink.
This throws me for a loop. Sort of like living in a cartoon world where
every action requires an equal and opposite wind-up.
Some months ago the notion was tossed out that perhaps spline interpolation
should be OFF as a default. I guess I will second that. Yet another jot
on the CUP horizon.
----------------------------------
Date: Wed, 24 Dec 1997 07:37:58 -0000
From: Richard Foster <RFosterTG@dial.pipex.com>
What from I gather spline interpolation "softens" transitions between key
frames. If the key frames are widely spaced or the transitions large,
Imagine has too much scope to interpolate and over softens. This can lead
to an actor move, rotate and scale further than intended before returning
to the value specified.
----------------------------------
Date: Wed, 24 Dec 1997 04:25:22 -0600
From: Mike Bayona <mb@MB.SIMPLENET.COM>
You can also get some weird effects by doing this: Set three key frames,
one in position A, two in position A, and three in position B. If you
watch the transition between one and two, the object will actually move,
even though the start and end points are the same.....because it has
created a spline that is bent because one end goes towards B, so the other
end is bent the other way. Sort of a built-in auto anticipation.
Really weird sometimes..... I made one animation where the camera was
supposed to slowly pan right across a view, instead it looked to the left
and then started panning.... :)
----------------------------------
Date: Thu, 1 Jan 1998 23:59:30 +0400
From: Charles Blaquiere <blaq@INTERLOG.COM>
Now back from Christmas with my family, I see your question has been
answered. I'd like to add a bit of explanation with that Blaq touch.
In Imagine, Action bars maintain their value in subsequent frames, until
a new Action bar appears to change that value. For example, if you set
the following keyframes:
#1 Frame 1 Size = 10,10,10
#2 Frame 10 Size = 30,30,30
#3 Frame 21 Size = 10,10,10
#4 Frame 30 Size = 30,30,30
and have your Actor bar disappear during frames 11-20, the Size bars
still behave on their own, as a spline curve with 4 keyframes. Imagine
will smooth out the changes from a size of 10 to 30 and back, creating a
nice spline morph.
In this case, you don't want Imagine to perform spline interpolation
between the second and third keyframe: you want Imagine to behave in the
first 10 frames as if there were no keyframes after #2; similarly, in
the last 10 frames Imagine should pretend there were no keyframes
preceding #3.
By activating the Discontinuous Knot checkbox on keyframe #2, you do
exactly that. Imagine will perform spline interpolation before #2 and
after #3 as if there were no keyframes on the other side to affect the
morph.
----------------------------------