Re: [Algorithms] Scale, camera, and world units and how it affects perception

[Stephen J B. <sj...@li...>]

On Fri, 14 Jul 2000, Kirk Hammond wrote:

> This has been something I have mulled for some time.  What _really_
> denotes scale in a 3D engine?  I currently run a ROAM based terrain
> engine with units like tanks, planes, yada yada.  Obviously the scale of
> objects moving by the viewer affects the perception of speed and size of
> a world unit.
> 
> So, this would lead one to believe that as long as you are consistent
> with your units (as I am), then everything would be fine.  And indeed,
> if I put a 2000 m cruiser in space and fly in a ship at 200 m/s it takes
> 10 sec to fly by the ship.  Fine and dandy.
 
Probiding you are utterly consistant and use the same units everywhere,
it doesn't matter what units you use.

> (e.g. if you have in the same 3D engine the view from an ant on the
> ground and a view from a human walking above...  aren't there viewport
> changes from the two vantages beyond moving the camera around and the
> fact that the camera is higher above the ground on the human?

Since you position the camera (and near/far clip planes) using the same
units that you use for drawing the scene, it won't matter.

> I mean,
> if the human stuck his eye on the ground level with the ant's viewpoint,
> doesn't the human still see more of the terrain than does the ant?)

No.  It seems that way because you physically can't get your head that
low - and your eyes won't focus that close (because they are so large).
But in OpenGL you don't have those nasty practical limitations - so it's
not a problem.

Steve Baker                      (817)619-2657 (Vox/Vox-Mail)
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