DXT compression explained - Revision history

BASys: /* External */

2009-11-14T16:14:42Z

External

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	== External ==		=== External ===
	[http://msdn.microsoft.com/en-us/library/bb204843(VS.85).aspx MSDN DirectX SDK Compressed Texture Resources]		[http://msdn.microsoft.com/en-us/library/bb204843(VS.85).aspx MSDN DirectX SDK Compressed Texture Resources]

2009-11-14T16:14:04Z

Added Texture link box

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	A second variant does interpolate only 4 other alpha values between the minimum and maximum, but also adds an alpha value of 0 and 1 (for fully transparent and not transparent). For some textures this might give better results.		A second variant does interpolate only 4 other alpha values between the minimum and maximum, but also adds an alpha value of 0 and 1 (for fully transparent and not transparent). For some textures this might give better results.

	~~== References ==~~

			== Related ==

			=== Internal ===
			{{Template:Navbox-Textur-Related}}

			== External ==
	[http://msdn.microsoft.com/en-us/library/bb204843(VS.85).aspx MSDN DirectX SDK Compressed Texture Resources]		[http://msdn.microsoft.com/en-us/library/bb204843(VS.85).aspx MSDN DirectX SDK Compressed Texture Resources]

2009-02-23T09:07:19Z

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2008-12-27T10:10:07Z

DXT5

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	== DXT5 ==		== DXT5 ==

			The DXT5 formats differs from the DXT3 format in the way the alpha information is saved. The colour information is stored in the same way.

			For the alpha information it uses a palette, similar to the way the colour information is also stored. This palette contains a minimum and maximum alpha value. Then 6 other alpha values are interpolated between this minimum and maximum. This thus allows more gradual changes of the alpha value.

			A second variant does interpolate only 4 other alpha values between the minimum and maximum, but also adds an alpha value of 0 and 1 (for fully transparent and not transparent). For some textures this might give better results.

	== References ==		== References ==

2008-12-27T09:44:17Z

← Older revision		Revision as of 04:44, 27 December 2008
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	== DXT5 ==		== DXT5 ==

			== References ==

			[http://msdn.microsoft.com/en-us/library/bb204843(VS.85).aspx MSDN DirectX SDK Compressed Texture Resources]

	[[Category:Texturing]]		[[Category:Texturing]]
	[[Category:Scenery_Design]]		[[Category:Scenery_Design]]
	[[Category:Aircraft_Design]]		[[Category:Aircraft_Design]]

2008-12-25T11:56:57Z

DXT3

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	== DXT3 ==		== DXT3 ==

			The colour information in DXT3 is saved similar to the DXT1 format without an alpha channel. So a palette of 4 colours is used to represent 16 pixels of the texture. But the alpha information is stored with 4 bit in the DXT3 format. That means that in total 128 bit are used for the 16 pixels (32 for the palette, 32 for the colour indices and 64 for the alpha information). So this results in a compression ratio of 1:4.

			Because the alpha information is stored in 4 bit, the smallest step in the alpha value that can be stored is 16. This means that very smooth transitions in the alpha channel can not be stored in the DXT3 format.

	== DXT5 ==		== DXT5 ==

2008-12-25T11:41:54Z

DXT1 with alpha

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	The other three colours are left to store the colour information of your pixels. So for the two colours stored in this case only one has to be interpolated, colour3 is 1/2 colour1 plus 1/2 colour2. This means even less resolution is left for different shades of colours.		The other three colours are left to store the colour information of your pixels. So for the two colours stored in this case only one has to be interpolated, colour3 is 1/2 colour1 plus 1/2 colour2. This means even less resolution is left for different shades of colours.

	~~''Todo: add some images to clarify what this means''~~

	== DXT3 ==		== DXT3 ==

2008-12-25T11:37:09Z

DXT1

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	\| [[Image:shades_red.jpg]]		\| [[Image:shades_red.jpg]]
	\|-		\|-
	\| ~~Bla bla bla~~		\| This image shows what happens when the different colour are not on a linear line in colour space. In this case all extremes (red, green and blue) have been used. It is clear the resulting interpolated colours not match the originals at all. Normally an area of 4x4 pixels would not have so wide variety of colours, but it illustrates that textures with many different colours are affected more.
	\| [[Image:shades_colour.jpg]]		\| [[Image:shades_colour.jpg]]
	\|}		\|}

2008-12-25T11:34:26Z

DXT1

2008-12-25T10:37:31Z

DXT1

← Older revision		Revision as of 05:37, 25 December 2008
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	Below are some images to clarify what the compression does to the quality of your texture. To make it more clear a region of 4x4 pixels has been blown up to a bigger size in the images.		Below are some images to clarify what the compression does to the quality of your texture. To make it more clear a region of 4x4 pixels has been blown up to a bigger size in the images.

	{\| ~~class~~="~~wikitable~~"		{\| border="0" cellpadding="5" cellspacing="5"
	\|-		\|-
	\| ~~Bla bla bla~~		\| This image shows how the compression affects colours. On the left you see 16 shades of red, ranging from pure red to pure black. On the right you see the four resulting colours that the DXT compression choose to represent these 16 pixels.
	\| [[Image:shades_red.jpg]]		\| [[Image:shades_red.jpg]]
	\|-		\|-