Difference between revisions of "Aspect ratio"

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(16:10 is standard terminology, even if it can be divided, almost nobody says 8:5.)
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[[Vanilla Doom]] runs in [[Wikipedia:VGA|VGA]] 320x200 mode, which is an 8:5 '''aspect ratio'''.  This causes problems on some modern computers which only support 4:3 ratio graphics modes.  Some [[source port]]s support aspect ratio correction, which attempts to remedy this.
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[[Vanilla Doom]] runs in [[Wikipedia:VGA|VGA]] 320x200 mode, which is an 16:10 '''aspect ratio'''.  This causes problems on some modern computers which only support 4:3 ratio graphics modes.  Some [[source port]]s support aspect ratio correction, which attempts to remedy this.
  
 
Almost all monitors have a physical size where the width and height of the screen are in a 4:3 ratio.  However, Vanilla Doom used a 320x200 screen resolution.  Because of the difference in aspect ratio between the screen resolution and the physical dimensions of the screen, the 320x200 screen is stretched.  The effect of this is that the pixels displayed on the screen are not square: they are each slightly taller than they are wide.
 
Almost all monitors have a physical size where the width and height of the screen are in a 4:3 ratio.  However, Vanilla Doom used a 320x200 screen resolution.  Because of the difference in aspect ratio between the screen resolution and the physical dimensions of the screen, the 320x200 screen is stretched.  The effect of this is that the pixels displayed on the screen are not square: they are each slightly taller than they are wide.
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; Graphical scaling : In this approach, the individual components of the screen are scaled to fit the 4:3 mode.  For example, the renderer is run in a way such that the game view is stretched to fit the screen.  Other graphics, such as the status bar, are drawn stretched.  A disadvantage to this approach is that some of the graphics (such as the status bar) may appear distorted due to the scaling. This is the approach taken by [[ZDoom]].
 
; Graphical scaling : In this approach, the individual components of the screen are scaled to fit the 4:3 mode.  For example, the renderer is run in a way such that the game view is stretched to fit the screen.  Other graphics, such as the status bar, are drawn stretched.  A disadvantage to this approach is that some of the graphics (such as the status bar) may appear distorted due to the scaling. This is the approach taken by [[ZDoom]].
  
; Whole-screen correction : With whole-screen correction, the screen is rendered to a 8:5 size.  The low-level graphics code then stretches the entire screen to fit the 4:3 graphics mode.  A disadvantage of this approach is that the screen may appear blurry due to the stretching.  This is the approach used by [[Chocolate Doom]] for aspect ratio correction.
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; Whole-screen correction : With whole-screen correction, the screen is rendered to a 16:10 size.  The low-level graphics code then stretches the entire screen to fit the 4:3 graphics mode.  A disadvantage of this approach is that the screen may appear blurry due to the stretching.  This is the approach used by [[Chocolate Doom]] for aspect ratio correction.
  
 
== Incorrect aspect ratio ==
 
== Incorrect aspect ratio ==
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== Choosing a graphics card ==
 
== Choosing a graphics card ==
  
The aspect ratio issue may be an important issue to Doom fans when choosing a graphics card, as support for the 320x200 mode seems to be mainly dependent on the graphics card manufacturer.  [[Wikipedia:NVIDIA|NVIDIA]] cards seem to properly support the 8:5 ratio modes, for example, while [[Wikipedia:ATI|ATI]] cards do not.
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The aspect ratio issue may be an important issue to Doom fans when choosing a graphics card, as support for the 320x200 mode seems to be mainly dependent on the graphics card manufacturer.  [[Wikipedia:NVIDIA|NVIDIA]] cards seem to properly support the 16:10 ratio modes, for example, while [[Wikipedia:ATI|ATI]] cards do not.
  
 
[[Category:Technical aspects]]
 
[[Category:Technical aspects]]
 
[[Category:Source ports]]
 
[[Category:Source ports]]

Revision as of 17:37, 14 June 2007

Vanilla Doom runs in VGA 320x200 mode, which is an 16:10 aspect ratio. This causes problems on some modern computers which only support 4:3 ratio graphics modes. Some source ports support aspect ratio correction, which attempts to remedy this.

Almost all monitors have a physical size where the width and height of the screen are in a 4:3 ratio. However, Vanilla Doom used a 320x200 screen resolution. Because of the difference in aspect ratio between the screen resolution and the physical dimensions of the screen, the 320x200 screen is stretched. The effect of this is that the pixels displayed on the screen are not square: they are each slightly taller than they are wide.

Some modern graphics cards and monitors only support 4:3 screen resolutions, and so Doom's native 320x200 resolution is not supported. In these cases, the screen may be displayed within a higher screen resolution, resulting in black borders at the top and bottom of the screen. For example, 320x200 mode games may actually run in 320x240 mode (a 4:3 resolution).

The effect of running with borders like this is that the screen appears squashed compared to the original Vanilla Doom, as everything physically appears 16% shorter. It appears that the doom graphics have been specifically designed for the 320x200 resolution; for example, the shape of the status bar face better matches the dimensions of a real human face when run in the stretched mode. Similarly, Cacodemons appear more round.

Aspect ratio correction

An aspect ratio-corrected version of the status bar face compared with the Mona Lisa and an uncorrected version. The version with aspect ratio corrected better matches the shape of the human face.

Some source ports include aspect ratio correction. This performs stretching of the screen's contents when running in a 4:3 screen mode, so that the graphics appear as they appeared in Vanilla Doom. This is generally accomplished in one of two ways:

Graphical scaling 
In this approach, the individual components of the screen are scaled to fit the 4:3 mode. For example, the renderer is run in a way such that the game view is stretched to fit the screen. Other graphics, such as the status bar, are drawn stretched. A disadvantage to this approach is that some of the graphics (such as the status bar) may appear distorted due to the scaling. This is the approach taken by ZDoom.
Whole-screen correction 
With whole-screen correction, the screen is rendered to a 16:10 size. The low-level graphics code then stretches the entire screen to fit the 4:3 graphics mode. A disadvantage of this approach is that the screen may appear blurry due to the stretching. This is the approach used by Chocolate Doom for aspect ratio correction.

Incorrect aspect ratio

The start of MAP01 as it appears in Doom 95. Compare with how this normally appears.

Some source ports do not handle 4:3 screen modes correctly. An example is Doom 95, which renders the screen with the wrong aspect ratio when running in 640x480 mode. The result is that the player can see more when running in 640x480 mode than in 320x200 or 640x400 mode.

Choosing a graphics card

The aspect ratio issue may be an important issue to Doom fans when choosing a graphics card, as support for the 320x200 mode seems to be mainly dependent on the graphics card manufacturer. NVIDIA cards seem to properly support the 16:10 ratio modes, for example, while ATI cards do not.