RE: [Algorithms] Smooth movement of camera along a path

[Robert D. <RD...@ac...>]

Just a quick note to say that one way to solve the problem of orientations
is to not use them at all, but instead interpolate your "target" along with
your camera, so that you just build a camera that looks at the target ...
which you would then naturally avoid tilting.  Of course if you _want_
tilting cameras this is no use whatsoever !

Rob

-----Original Message-----
From: Peter Warden [mailto:Pet...@vi...]
Sent: 01 August 2000 12:40
To: gda...@li...
Subject: RE: [Algorithms] Smooth movement of camera along a path


I've done a couple of similar systems, and I've found the problem to be
deceptively tricky, a few things I ran across that weren't obvious to me
when I started;

-Whatever spline you pick to move the camera's position, you'll need to be
aware that changing the parameter to the spline isn't proportional to
distance along the spline, eg a u parameter of 0.5 may correspond to a point
that's only 0.25 of the total distance along the spline. This means that
some compensation will be needed if you want the camera to move at a
constant speed, or to accelerate and decelerate under your control. One
solution I used was to sample the spline at many points, and construct a
series of (very small) straight lines to represent the spline. This let me
do distance calculations and get smooth movement, at the cost of being a bit
inelegant. Advanced Animation and Rendering Techniques, Watt&Watt, 15.3.2
has a good discussion of this, and some other ways of solving the problem.

-Splines will solve the movement problem, but not necessarily the
orientation one. Interpolation between orientations is a big subject, and
took a lot more time than I expected!

-It's not just a maths problem, there's a lot of quirky human stuff that
needs to taken into account to get a camera moving in a way that people will
like. A good example of this is interpolating orientations, it's very easy
to end up with interpolated orientations that are tilted in uncomfortable
ways.

Having been a wet blanket with all this, I would say on the positive side
that adding extra keyframes so you aren't putting too much strain on the
interpolation code solves a lot of the problems, and most others can be
solved by working around them.

AA&RT, Watt and Watt, is an excellent source for info on the subject.

Peter Warden

> -----Original Message-----
> From: Mark Wilczynski [mailto:mwi...@cy...]
> Sent: Monday, July 31, 2000 11:04 PM
> To: gda...@li...
> Subject: [Algorithms] Smooth movement of camera along a path
> 
> 
> I'm trying to write a fly-by sequence (similar to the Unreal
> intro) for my 3d engine.  Can anyone tell me how to smoothly
> move the camera along a set of predefined 3d points?
> Ideally,  I would like a system where I manually move the
> camera around the environment and record keyframes at
> certain positions/orientations.  Then I would like the
> system to automatically move the camera along a path
> interpolated from these keyframes.  I'm guessing I need some
> sort of spline or other curve to do the job?
> 
> -Mark
> 
> 
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