What it is & when and how to use it.
When displayed on modern graphics hardware with square-pixels, 4:3 screen mode (640x480) and the same number of rows of pixels, these same graphics will appear distorted (unnaturally compressed vertically to a 16:10 aspect ratio) and letterboxed with black bars above and below. The graphics do not look as the developer intended.
To preserve the original 4:3 ratio as the developer intended, the graphics need to be stretched vertically. This is the purpose of aspect correction. The aspect correction setting in DOSBox and ScummVM will extrapolate extra rows to extend the height and restore the 4:3 aspect ratio. Note that on modern wide screen monitors the game will be pillarboxed, but the game will be displayed properly.
This distortion affects all of the graphics. Note how Graham's face looks oddly roundish without the correction while aspect correction removes this distortion. The shape of his head is closer to that of a real person's face.
Note that aspect correction is not always needed and sometimes cannot be set for one reason or another. The Sierra VESA era games used 640x480 resolution (4:3) if the VESA.DRV is set for the videoDrv setting in the game's configuration file (RESOURCE.CFG) and thus aspect correction is not needed. The ScummVM team disabled aspect correction for King's Quest VI Windows version for technical reasons for the intro AVIs to play properly. Some fan made SCI games were designed for a 16:10 ratio by not using aspect correction, so these games should not have aspect correction set. (also http://sciprogramming.com/fangames.php?eng=both )
To turn on aspect correction in DOSBox, under the [render] section of the dosbox.conf set:
Code: Select all
Then enjoy your game as Sierra intended.