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Author Topic: "Bilinear plus" filter  (Read 3509 times)
geoslake
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"Bilinear plus" filter
« on: November 09, 2007, 02:48:16 pm »

hi, and thanks for the amazing port of this amazing game  Grin

just wonder, while the filters are already very nice, could you consider ading the "bilinear plus" one
shot here :
http://img212.imageshack.us/my.php?image=bilinpluszv1.png

its used in exult engine, visual boy advance...and looks very good to me
thanks
« Last Edit: November 09, 2007, 02:49:50 pm by geoslake » Logged
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Re: "Bilinear plus" filter
« Reply #1 on: November 11, 2007, 05:28:19 pm »

Looks like a rather simple variant of bilinear to me. Start with a typical bilinear filter, where each pixel (a in this example) is expanded to four pixels (s, t, u and v) based on the neighbouring pixels (b, c, d):

Code:
a|b => st|
--     uv|
c d    ---

The classic bilinear goes:
Code:
s=a
t=(a+b)/2
u=(a+c)/2
v=(a+b+c+d)/4

Bilinear plus, in Exult, appears to substitute:
Code:
s=(5*a+b+c)/8
This would give a slight "dark dot-matrix" effect, as seen on the screenshot (checked by eye, not mathematically).

Or, in the "original" (dot-matrix-less) version:
Code:
s=(5*a+2*b+c)/8
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countchocula86
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Re: "Bilinear plus" filter
« Reply #2 on: November 11, 2007, 08:05:21 pm »

Im kinda confused by what this discussion is about? Is this "bilinear filter" a way of resizing or something? So confused lol
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Re: "Bilinear plus" filter
« Reply #3 on: November 11, 2007, 09:33:15 pm »

You could always put in the request through the bug database as an enhancement. It may get picked up sooner or later then.
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Re: "Bilinear plus" filter
« Reply #4 on: November 11, 2007, 11:03:11 pm »

I do like this filter. It's from the VisualBoyAdvance, correct?.
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Re: "Bilinear plus" filter
« Reply #5 on: November 11, 2007, 11:23:09 pm »

Im kinda confused by what this discussion is about? Is this "bilinear filter" a way of resizing or something? So confused lol
Exactly. The graphics in 3DO SC2 are at a resolution of 320x240 pixels. By modern standards (and on modern monitors), this results in some very blocky (or, with some modern LCD monitors, very blurry) graphics in fullscreen mode (or a tiny window at desktop resolutions). In order to mitigate this, UQM (optionally) rescales the graphics up to 640x480 using a wide range of 2x scalers (implemented in software) and then (again, optionally) rescales the graphics using OpenGL bilinear interpolation to the screen or window resolution (which may require fractional scaling, which would be a bit on the slow side in software).

The scalers (often referred to as "filters") supported by UQM (see Setup/Graphics Options) are:
  • Nearest ("none"): Each pixel converted into a 2x2 block of the same colour. Quick but looks awful.
  • Bilinear: Slightly different in UQM to the version I described above. In both cases, each output pixel is interpolated linearly in both X and Y directions from the neighbouring original pixels (4 of them). The Exult variant places the output pixels at (0,0), (0,0.5), (0.5,0) and (0.5,0.5) relative to the original pixels, UQM uses (0.25,0.25), (0.75,0.25), (0.25,0.75) and (0.75,0.75) instead (resulting in a blurrier look).
  • Biadapt: Like bilinear, but tries to maintain sharp edges by using the sharper version of bilinear and changing the bottom-right pixel in each block if it's in the middle of a diagonal line of solid colour.
  • Biadv: Like biadapt, but with more special cases (lines at other angles).
  • Triscan: uses pixels above and below (and left and right) to check for edges (highly dissimilar colours). Outside edges, just copy the pixel to a 2x2 block. On edges, blend diagonally pixels that seem to be on the same side of the edge.
  • HQ2x: Check whether all 8 neighbouring pixels are similar in colour and use a carefully set-up table of best guesses of what each combination means in terms of edges to determine what should be there.
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geoslake
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Re: "Bilinear plus" filter
« Reply #6 on: November 13, 2007, 07:45:55 am »

You could always put in the request through the bug database as an enhancement. It may get picked up sooner or later then.

you mean theres zero probability the developers will look at this thread ?
Posting it as a bug wouldnt please me...
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Re: "Bilinear plus" filter
« Reply #7 on: November 13, 2007, 12:16:09 pm »

They do look at it and if they like it, they may actually take action upon it. They got lives too however and if the request is a "single user" one, there's may not be much enthusiasm to create it, let alone remember that someone might actually be interested in it. The Bug database at least makes sure that your request is read at least once and if it has merit, may be picked up eventually (it helps a lot if you can create a working concept too by the way).

EDIT: the term "Bug database" is not entirely correct. It can be used to post enhancements as well. Just set the priority to enhancement.
« Last Edit: November 13, 2007, 01:51:46 pm by Koowluh » Logged

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Re: "Bilinear plus" filter
« Reply #8 on: November 14, 2007, 07:01:31 pm »

Added to Bugzilla as bug 1020.
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geoslake
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Re: "Bilinear plus" filter
« Reply #9 on: November 17, 2007, 12:31:50 pm »

thanks for having it added  Smiley
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