Moved this topic over from the binaries.animation group, the Men in
Mustangs thread. Question arises as to getting slight motion offsets of
multiple independantly moving objects. 

I just happened to think, I said identical rotations of the prop and that
relates to a problem with differing object motions through the course of
animation. Everthing has to be in a ratio where the slowest moving thing
has to be the basis for the rest (maybe). Get what I mean here? I've done
quite a few animations, even a watch dial one, and if you were to try it
at all I don't see it as being possible without some math to sort it out.
After all, it would be fractions of rotation needed. Like the four blades
need only a 1/4 rotation to look like a full rotation. The faster prop
would need to go half turn and a faster yet one 3/4 turn. Problem here is
that would seem way different between them and what you'd want if anything
at all would be a 1/16 or less, the blades would not align properly (pun,
or not?) without making a further rotation of the slowest to match up.
Think about it, can it really be done?
I realize this depends upon number of frames a lot too, but has anyone a
method for doing most any such situation. I'm sure it's been discussed
before, I'll just reopen the discussion here.


-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/homepage.htm
 mailto://inversez@aol.com?Subject=PoV-News

Post a reply to this message

Bob Hughes wrote:
> 
> Moved this topic over from the binaries.animation group, the Men in
> Mustangs thread. Question arises as to getting slight motion offsets of
> multiple independantly moving objects.
> 
> I just happened to think, I said identical rotations of the prop and that
> relates to a problem with differing object motions through the course of
> animation. Everthing has to be in a ratio where the slowest moving thing
> has to be the basis for the rest (maybe). Get what I mean here?

  I see where you are going with this Bob I can understand the
pitfall of this logic. Instead of catering to the slowest object
in the scene you instead must build around the fastest objects
in the scene.
  Say for example you tare trying to make prop spin fast enough
in an animation to actually blur the blades a bit. You can't
simply say to the prop "spin faster" and expect it to work.
Instead you must insure that you have a high enough frame rate
that you can move the prop in tiny increments so as to smooth
out it's appearance.
  All of the other objects in the scene need only a fraction
of the clock so you can have them doing anything you want in
the mean time. For slower objects you can simply divide the
frames count by a suitable amount and divide your objects
animation function with this number accordingly. You can't
on the other hand make an object go realistically fast in a
very short frame animation with having it look like it was
warping from one place to the next.
  Don't forget that the guys that make video images of bullets
slowly going through a beer bottle or those guys that actually
capture a hummingbirds wings in almost stop motion are using
film speeds of 20,000 to 120,000 frames per sec. I just saw
a special on TV a month ago about a guys work in this field
and he has a new camera on order that allegedly will hit
150,000 frames/sec. I stand in disbelief that this even
possible but then again raytracing seem fast enough to me :)

-- 
Ken Tyler

mailto://tylereng@pacbell.net

Post a reply to this message

Yeah, I think the earliest form of  high speed cameras was work by Edison.
:)
uh, both the camera and photography. heh

GrimDude
vos### [at] arkansasnet

Post a reply to this message

The way I have M.I.M. right now is just simple stuff. The prop is a
uniform rotation, and the cyclic turbulence is a simple transformation. I'm
sure there are numerous things you could do, but I settled on:

translate <0,sin(clock*2*pi)*.006,(cos(-clock*2*pi)*.007)>

as a typical start.That should be enough to make forward motion look right,
but note that in my posted animation I used a single clock period for 180
degrees of rotation (with respect to the prop), and 360 degrees for the
translation, and now I intend to go to 30 frames/sec for mpeg, so everything
comes out right.

I need a function to change the prop texture dependant upon "angle_off" the
camera. Hmm,... Then as I speed things up by putting the aircraft into
attack mode, the props will speed up. The texture will change and become
more blurry, for instance, and the pilot heads rotate at fewer intervals
(oops, did I forget to mention that?).

Working on the rocket rails now (ordinance tree). I went out and found a
Discovery CDRom, recently, that had a short animation of 51 dropping tanks
and peeling off. I can't share it, but I can emulate it. :)

GrimDude
vos### [at] arkansasnet

Post a reply to this message

Okay, just posted a 24fps 25 frame b&w for comparison. I think I like 75
frames at the same rate.

GrimDude
vos### [at] arkansasnet

Post a reply to this message