Re: [TuxKart-devel] Patch for smooth camera motion...

[Steve B. <sjb...@ai...>]

Kevin Cowtan wrote:
> 
> Steve Baker wrote:
> > Do you think the 0.2 and 0.1's here should actually be somehow
> > related to the time delta between frames?
> >
> > > !     steady_cam.xyz[0] = steady_cam.xyz[0] + 0.2f*diff.xyz[0];
> > > !     steady_cam.xyz[1] = steady_cam.xyz[1] + 0.2f*diff.xyz[1];
> > > !     steady_cam.xyz[2] = steady_cam.xyz[2] + 0.2f*diff.xyz[2];
> > > !     steady_cam.hpr[0] = steady_cam.hpr[0] + 0.1f*diff.hpr[0];
> > > !     steady_cam.hpr[1] = steady_cam.hpr[1] + 0.1f*diff.hpr[1];
> > > !     steady_cam.hpr[2] = steady_cam.hpr[2] + 0.1f*diff.hpr[2];
> >
> > It seems like this would look different on a high frame rate machine
> > than on a low rate system.
> 
> Oh yes, you are absolutely right. The values either need to be scaled
> proportionally to the time since the last frame, or there needs to be
> some sort of time based history mechanism (which I presume is what your
> cart history does).

Yep - I just need to change those 0.1/0.2 values into <something>*delta_t
Those hard-coded numbers seem to look good at ~30Hz frame rate - so
<something> should be about 30*0.1 and 30*0.2 or so.

> I initially meant to have a look and see if this routine was driven off
> a timer or off the frame update, and then didn't get round to it.

It's executed once per frame (unless you have a VERY slow PC) and the
timer sets delta_t to ensure your speed is not affected by the frame
rate.
 
> Also, from the code, it looks like there is the possibility
> (unimplemented?) of flipping the view between karts. My patch will cause
> the camera to spin erratically through walls if this happens.

Actually, it is implemented - page-up and page-down steps through a
number of fixed cameras and each of the karts in turn.  It's useful
when debugging (eg "Gown doesn't seem to be moving anymore - I wonder
what went wrong" - I can move the camera to follow her and see why 
she's driving around in circles or whatever).

We should implement that properly and have a 1st person view, a
far distant view, a close up view and a view looking backwards
or something.
 
It won't be hard to fix your code so that the camera can
'teleport' between views rather than interpolating it's
way across half the 'world'.

-- 
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