[GEM-dev] AA with shader

Mathieu Bouchard matju at artengine.ca
Fri Jan 28 16:44:48 CET 2011


On Fri, 28 Jan 2011, cyrille henry wrote:

> for AA in a FB, i also have good result rendering 4 time the same pimitive 
> with alpha and displaced by 1/2 pixel in each direction.

Proper AA would render 4 times the same primitive displaced by (0 0), (0 
1/2), (1/2 0), and (1/2 1/2), instead, so that the 4 points form a square 
aligned with the pixel grid, instead of at 45°.

Also, care must be taken to ensure 25 % contribution of each layer (and 
not some other percentage sequence if you use a normal [alpha] with 75 % 
opacity in all four layers). Thus you use opacity 100 %, 50 %, 33,333 %, 
25 %, from the bottom up (that's 1/n).

But in any case, it's a good idea.

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| Mathieu Bouchard ---- tél: +1.514.383.3801 ---- Villeray, Montréal, QC


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