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Keyframe_Improvement
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1998-02-16
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Date: Sat, 27 Dec 1997 16:42:32 -0600
From: "Stephen G." <sgiff@AIRMAIL.NET>
Subject: [IML] IFW: Keyframe Improvement
I am sure many of you have found that when keyframing object movment you
may begin to set the desired keyframed positions and then after going back
you see that keyframed path is causing objects to travel out of boundaries
that you were expecting. This means you need to go back and add other keys
inbetween the original ones to force the movement back into a desired
trajectory. The problem is that you then have to decide how many frames in
between each key will keep your object moving at the same rate of travel.
This is difficult unless you can choose a keyframe in the middle, but this
is not always possible if you want the path to be confined to tight curves.
The current implementation of keyframing has two major problems in my
opinion which add a lot of extra time in trying to create smooth motion.
1. The path of the keyframe is automatically generated by Imagine which
usually results in undesired movement of objects.
2. If you need to go back and insert additional keyframes in a smooth
motion segment, it is impossible to determine at what frame and at which
point in the current trajectory or path the new keyframe should be inserted
because if you select one at random, you lose the contiguous motion that
was originally there.
I have included examples of this problem and the solution here:
http://web2.airmail.net/sgiff/images/keyframe.jpg
There are those who will argue that you can always create a path in the
Stage and edit the path but if you have ever tried to create a complex
banks and curves, you know it is difficult. Furthermore, keyframing by
moving objects is simple and much faster. and forces any object to move
along the path at one rate without the ability to keyframe positions along
the path should you desire.
---------------------------------
Date: Sun, 28 Dec 1997 21:09:42 -0800
From: Mike McCool <mikemcoo@EFN.ORG>
Hey Stephen,
I may be 180 degrees off here, but my hit on this prob is that it
has to do with the way Imagine interprets (interpolates) the splines of
the path.
In another mandelbrot renderer that shall remain nameless, there's
an easy way to assure that what you set in a keyframe is what you get.
You simply set spline interpolation as LINEAR, and you'll get EXACTLY the
path you set.
Disadvantage of this--and the elegance of the way Imagine
interpolates splines,--is that your objects can jerk about
unrealistically, if there are drastic changes of direction.
(I've tried various settings of spline interpolation, in Imagine's
action editor bar, to get objects to stay true to the path I've assigned).
Again, if this is no help to your prob, please excuse the width.
Jerking smoothly on path,
---------------------------------
Date: Mon, 29 Dec 1997 04:42:03 -0600
From: Mike Bayona <mb@MB.SIMPLENET.COM>
First off, SG, I got your original post, but didn't reply because I knew
what would happen if I did....
> I am
>sure it is something that will be added in future versions.
>I think the same could be true of velocity scaling, namely some graphical
>way of controlling these wonderfully useful options.
While you may be sure, I remain doubtful... My reason is simple. Item
#89 on the Animation CUP Feature Vote Page, by Tom Delaney is "Editable
Function Curves" check out Mike H's response in red on the page.
http://homepage.midusa.net/~toto/misc/editable.htm
---------------------------------
Date: Thu, 1 Jan 1998 23:28:14 +0400
From: Charles Blaquiere <blaq@INTERLOG.COM>
Stephen G. wrote:
>
> http://web2.airmail.net/sgiff/images/keyframe.jpg
Stephen, I agree that, currently, Imagine's spline interpolation creates
uncertainty as a side effect. One "band-aid" way Impulse could alleviate
the situation, without changing the entire morph algorithm or adding a
full visual interface, could be to have a "Show motion path" Object menu
item. This would have Imagine compute the selected actor's motion
through the entire project, and display the result in the four views as
a path, with a dot placed along the path at every keyframe. The dots
could help you judge where to define additional keyframes without overly
disturbing the object's velocity. (You'd activate Bluing to preserve the
visible path as you flip to the relevant frames)
Come to think of it, this beings up a technique I've used in the past,
to display an object's motion:
- Use Hide Layers to remove unnecessary objects from view;
- Go to the first frame;
- Activate Bluing and Quick Stage;
- Flip through all the frames in the animation.
The result shows a composite of all the positions my object has
occupied. If you wanted a simpler display, you could temporarily resize
the object to a small value to have its bounding box approximate a large
dot, or you could add a small axis to the scene, position it atop the
object on the first frame, Associate the axis to the object, and hide
all but the axis; it would follow the same motion as the object, but its
small bounding box would also approximate a large dot.