Scott Long wrote: > > On Tue, 12 Nov 2002 15:09:37 +0100 > David Balazic <[EMAIL PROTECTED]> wrote: > > >I've been toying with this idea to use the video overlay feature > >as an efficient anti alias method. Is this doable ? > > > >Here is how it would work : > > > >set the display to some resolution ( higher is better ) > >render your picture ( at a lower , same or higher resolution than > >the > >display ) > >use the overlay to scale the picture to the physical screen > > > >cards with good scaling ( filtering etc. ) would make a nice > >smoothed picture , right ? > > The only option you mention that could possibly work would be to > render the image at a *higher* resolution than the display resolution, > then scale the image down using coverage-weighted averaging. This is > known as "supersampling" and is how many AA algorithms work.
So is this doable or not ? > Your other options would make the image "smoother," but only because > they would blur the image. More smooth == less alias , or am I missing something ? > You can't resize an image to a larger size > and get more detail out of nothing. And we don't want more detail, just less alias. > The only effect a filter would > have would be to smear the image. > > >Examples of use : > > > > - text anti-alias : > > render the text at lower resolution, then scale it up > > to some higher resolution, and get AA filtering for "free" > > > > - 3D FSAA : render at higher resolution, scale down to get FSAA > > ( using the same resolution ( 1:1 scaling ) might give something > > useful too ? ) > > > >Opinions ? > > Unfortunately, that won't work at all. What you want to do is render > the text at a *higher* resolution and then scale the result *down* to > the display resolution using coverage-weighted averaging. You can't > get anything for free! If you tried what you suggest, what you'd end > up with would be a blocky character that shows stairstepping, except > the stairsteps would be blurry. Not only ugly, but a headache-inducer > :-) I think proper filtering would remove the stairs ( the low res ones, the high res ones ( the final image ) depend on the way the RAM-DAC operates ) > There are many (and *much* better) techniques for antialiasing fonts > in particular that don't resort to this brute-force supersampling > method. > > Scott Long > SwiftView, Inc. http://www.swiftview.com > _______________________________________________ > Xpert mailing list > [EMAIL PROTECTED] > http://XFree86.Org/mailman/listinfo/xpert _______________________________________________ Xpert mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/xpert
