Perspective Transform (was: Screen shots for Squeak.org)

Bert Freudenberg bert at isgnw.CS.Uni-Magdeburg.De
Sun Jun 20 11:00:58 UTC 1999


On 19 Jun 1999, Lawson English wrote:

> One thing missing from all the current graphics engines is the ability to
> apply perspective. 

I'm not really sure what you mean by this - almost every 3D graphics
engine has this ability: it's called texture mapping. And why would we
want to have perspective distortion if we do not go three-dimensional?

> I have a rough idea how to do it*, but I'm not sure how useable it would
> be in Squeak without creating C-primitives that support it. 
> 
> However, it if IS doable, it would certainly make Squeak more powerful
> than anything else out there. 

It's already there!  Almost, that is. Balloon3D is able to display a
bitmap (Form)  with perspective.  So you could have it display a window's
form as easily as a loaded bitmap.  What's missing is the ability to make
this view respond to mouse/key events in the same way as it does in the
2D-World.  Just imagine some arbitrary Morph being dropped into a
Wonderland and living there happily on ...

> *cache the line-segments of a bezier path as it would be drawn without
> perspective, and then apply the perspective to each line segment. This
> strategy works well, but probably requires efficient (C-based) access to
> the cached info in order to run in real-time. 

IMHO this would be too specific, the texture mapping approach is more
general.

Cheers,
/bert

-- 
 Bert Freudenberg                                       Department of 
                                                        Simulation and
                                                        Computer Graphics
 http://isgwww.cs.uni-magdeburg.de/isg/bert.html        Univ. of Magdeburg





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