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

[Peter W. <Pet...@vi...>]

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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