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

[Pallister, K. <kim...@in...>]

I don't see how the lookattarget thing will solve the orientation problem.
You still need an 'up' vector, as you could be rotated any way around the
lookattarget vector.

While on the subject, as long as you are implementing splines for your
cameras, and these splines are to be modelled by artists, you may want to
think about having separate camera and target splines. We had this in a 3D
CAD driver I once worked on, and it was cool because you could do things
like have a whole number of keyframes on the target path, all sitting at an
interesting object, and then have the camera turn during it's 'flyby' to
focus on a specific area while maintaining it's speed.

Kim Pallister

We will find a way or we will make one.
                     - Hannibal


> -----Original Message-----
> From: Robert Dibley [mailto:RD...@ac...]
> Sent: Wednesday, August 02, 2000 2:11 AM
> To: 'gda...@li...'
> Subject: RE: [Algorithms] Smooth movement of camera along a path
> 
> 
> 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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