Normal Map Compression - Revision history

EricChadwick: swizzle

2016-04-28T13:47:19Z

swizzle

EricChadwick: links to swizzling, dxt, dtx5

2016-04-28T13:46:22Z

links to swizzling, dxt, dtx5

EricChadwick: Normal Map isn't a category

2016-04-28T13:44:10Z

Normal Map isn't a category

EricChadwick: categories fixed

2016-04-28T13:43:36Z

categories fixed

EricChadwick: Link to normal map

2015-05-17T22:15:10Z

Link to normal map

EricChadwick: channel packing

2015-03-29T13:30:33Z

channel packing

Cman2k at 08:24, 29 November 2014

2014-11-29T08:24:24Z

Cman2k: Created page with "NOTOC Normal maps can take up a lot of memory. Compression can reduce the size of a map to 1/4 of what it was uncompressed, which means you can either increase the resolut..."

2014-11-29T08:22:15Z

Created page with "__NOTOC__ Normal maps can take up a lot of memory. Compression can reduce the size of a map to 1/4 of what it was uncompressed, which means you can either increase the resolut..."

New page

__NOTOC__
Normal maps can take up a lot of memory. Compression can reduce the size of a map to 1/4 of what it was uncompressed, which means you can either increase the resolution or you can use more maps.

Usually the compression method is to throw away the Blue channel, because this can be re-computing at minimal cost in the shader code. Then the bitmap only has to store two color channels, instead of four (red, green, blue, and alpha).

* The article [http://developer.download.nvidia.com/whitepapers/2008/real-time-normal-map-dxt-compression.pdf Real-Time Normal Map DXT Compression] (PDF) from [http://www.idsoftware.com/ id software] and [http://developer.nvidia.com NVIDIA] is an excellent introduction to compression.

== DXT5nm Compression ==
DXT5nm is the same file format as DXT5 except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called ''swizzling''.

The Green and Alpha channels are used because in the DXT format they are compressed using somewhat higher bit depths than the Red and Blue channels. Red and Blue have to be filled with the same solid color because DXT uses a compression system that compares differences between the three color channels. If you try to store some kind of texture in Red and/or Blue (specular power, height map, etc.) then the compressor will create more compression artifacts because it has to compare all three channels.

There are some options in the NVIDIA DXT compressor that help reduce the artifacts if you want to add texture to the Red or Blue channels. The artifacts will be greater than if you keep Red and Blue empty, but it might be a tradeoff worth making. Some notes about this on the [http://developer.nvidia.com/forums/index.php?showtopic=1366 NVIDIA Developer Forums].

== DXT1 Compression ==
DXT1 is also used sometimes for tangent-space normal maps, because it is half the size of a DXT5. The downside though is that it causes many more compression artifacts, so much so that most people end up not using it.

* The blog post [http://realtimecollisiondetection.net/blog/?p=28#more-28 I like spilled beans!] by [http://realtimecollisiondetection.net/blog/?page_id=2 Christer Ericson] has a section about Capcom's clever use of DXT1 and DXT5.

== 3Dc Compression ==
3Dc compression is also known as BC5 in DirectX 10. It works similar to DXT5nm, because it only stores the X and Y channels. The difference is it stores both the same way as the DXT5 Alpha channel, which is a slightly higher bit depth than DXT5nm's Green channel. 3Dc yields the best results of any listed algorithm for tangent space normal map compression, and requires no extra processing time or unique hardware. See [[3Dc]] for more information.

== [[A8L8]] Compression ==
The DDS format !A8L8 isn't actually compressed, it's just two 8bit grayscale channels (256 grays each). It does save you from having to store all three color channels. Your shader has to recompute the blue channel for it to work. However, !A8L8 does not actually save any space in texture memory, it is typically converted to a four-channel 32bit texture when it's sent to the card. This format really only helps save disk space.

@@ Line 7: / Line 7: @@
 == DXT5nm Compression ==
-DXT5nm is the same file format as [[DXT#DXT5|DXT5]] except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called [[ChannelPacking#Swizzling|swizzling]].
+DXT5nm is the same file format as [[DXT#DXT5|DXT5]] except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called [[ChannelPacking#Swizzle|swizzling]].
 The Green and Alpha channels are used because in the [[DXT]] format they are compressed using somewhat higher bit depths than the Red and Blue channels. Red and Blue have to be filled with the same solid color because DXT uses a compression system that compares differences between the three color channels. If you try to store some kind of texture in Red and/or Blue (specular power, height map, etc.) then the compressor will create more compression artifacts because it has to compare all three channels.
@@ Line 21: / Line 21: @@
 == 3Dc Compression ==
-Dc compression is also known as BC5 in DirectX 10. It works similar to DXT5nm, because it only stores the X and Y channels (see [[ChannelPacking]]). The difference is it stores both the same way as the DXT5 Alpha channel, which is a slightly higher bit depth than DXT5nm's Green channel. 3Dc yields the best results of any listed algorithm for tangent space normal map compression, and requires no extra processing time or unique hardware. See [[3Dc]] for more information.
+Dc compression is also known as BC5 in DirectX 10. It works similar to DXT5nm, because it only stores the X and Y channels (see [[ChannelPacking#Swizzle|Swizzle]]). The difference is it stores both the same way as the DXT5 Alpha channel, which is a slightly higher bit depth than DXT5nm's Green channel. 3Dc yields the best results of any listed algorithm for tangent space normal map compression, and requires no extra processing time or unique hardware. See [[3Dc]] for more information.

@@ Line 7: / Line 7: @@
 == DXT5nm Compression ==
-DXT5nm is the same file format as DXT5 except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called ''swizzling'' or [[ChannelPacking|channel packing]].
+DXT5nm is the same file format as [[DXT#DXT5|DXT5]] except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called [[ChannelPacking#Swizzling|swizzling]].
-The Green and Alpha channels are used because in the DXT format they are compressed using somewhat higher bit depths than the Red and Blue channels. Red and Blue have to be filled with the same solid color because DXT uses a compression system that compares differences between the three color channels. If you try to store some kind of texture in Red and/or Blue (specular power, height map, etc.) then the compressor will create more compression artifacts because it has to compare all three channels.
+The Green and Alpha channels are used because in the [[DXT]] format they are compressed using somewhat higher bit depths than the Red and Blue channels. Red and Blue have to be filled with the same solid color because DXT uses a compression system that compares differences between the three color channels. If you try to store some kind of texture in Red and/or Blue (specular power, height map, etc.) then the compressor will create more compression artifacts because it has to compare all three channels.
 There are some options in the NVIDIA DXT compressor that help reduce the artifacts if you want to add texture to the Red or Blue channels. The artifacts will be greater than if you keep Red and Blue empty, but it might be a tradeoff worth making. Some notes about this on the [http://developer.nvidia.com/forums/index.php?showtopic=1366 NVIDIA Developer Forums].

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−	[[Normal Map]] [[:Category:Texturing]] [[:Category:TextureTypes]] [[:Category:Bump map]]	+	[[Normal Map]] [[Category:Texturing]] [[Category:TextureTypes]] [[Category:Bump map]]

← Older revision		Revision as of 08:24, 29 November 2014
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	== [[A8L8]] Compression ==		== [[A8L8]] Compression ==
	The DDS format !A8L8 isn't actually compressed, it's just two 8bit grayscale channels (256 grays each). It does save you from having to store all three color channels. Your shader has to recompute the blue channel for it to work. However, !A8L8 does not actually save any space in texture memory, it is typically converted to a four-channel 32bit texture when it's sent to the card. This format really only helps save disk space.		The DDS format !A8L8 isn't actually compressed, it's just two 8bit grayscale channels (256 grays each). It does save you from having to store all three color channels. Your shader has to recompute the blue channel for it to work. However, !A8L8 does not actually save any space in texture memory, it is typically converted to a four-channel 32bit texture when it's sent to the card. This format really only helps save disk space.
		+
		+	----
		+	[[Normal Map]] [[:Category:Texturing]] [[:Category:TextureTypes]] [[:Category:Bump map]]

@@ Line 1: / Line 1: @@
-__NOTOC__
+[[Normal map]]s can take up a lot of memory. Compression can reduce the size of a map to 1/4 of what it was uncompressed, which means you can either increase the resolution or you can use more maps.
-Normal maps can take up a lot of memory. Compression can reduce the size of a map to 1/4 of what it was uncompressed, which means you can either increase the resolution or you can use more maps.
 Usually the compression method is to throw away the Blue channel, because this can be re-computing at minimal cost in the shader code. Then the bitmap only has to store two color channels, instead of four (red, green, blue, and alpha).

@@ Line 8: / Line 8: @@
 == DXT5nm Compression ==
-DXT5nm is the same file format as DXT5 except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called ''swizzling''.
+DXT5nm is the same file format as DXT5 except before compression the red channel is moved into the alpha channel, the green channel is left as-is, and the red and blue channels are blanked with the same solid color. This re-arranging of the normal map axes is called ''swizzling'' or [[ChannelPacking|channel packing]].
 The Green and Alpha channels are used because in the DXT format they are compressed using somewhat higher bit depths than the Red and Blue channels. Red and Blue have to be filled with the same solid color because DXT uses a compression system that compares differences between the three color channels. If you try to store some kind of texture in Red and/or Blue (specular power, height map, etc.) then the compressor will create more compression artifacts because it has to compare all three channels.
@@ Line 22: / Line 22: @@
 == 3Dc Compression ==
-Dc compression is also known as BC5 in DirectX 10. It works similar to DXT5nm, because it only stores the X and Y channels. The difference is it stores both the same way as the DXT5 Alpha channel, which is a slightly higher bit depth than DXT5nm's Green channel. 3Dc yields the best results of any listed algorithm for tangent space normal map compression, and requires no extra processing time or unique hardware. See [[3Dc]] for more information.
+Dc compression is also known as BC5 in DirectX 10. It works similar to DXT5nm, because it only stores the X and Y channels (see [[ChannelPacking]]). The difference is it stores both the same way as the DXT5 Alpha channel, which is a slightly higher bit depth than DXT5nm's Green channel. 3Dc yields the best results of any listed algorithm for tangent space normal map compression, and requires no extra processing time or unique hardware. See [[3Dc]] for more information.
-== [[A8L8]] Compression ==
+== A8L8 Compression ==
-The DDS format !A8L8 isn't actually compressed, it's just two 8bit grayscale channels (256 grays each). It does save you from having to store all three color channels. Your shader has to recompute the blue channel for it to work. However, !A8L8 does not actually save any space in texture memory, it is typically converted to a four-channel 32bit texture when it's sent to the card. This format really only helps save disk space.
+The DDS format A8L8 isn't actually compressed, it's just two 8bit grayscale channels (256 grays each). It does save you from having to store all three color channels. Your shader has to recompute the blue channel for it to work. However, A8L8 does not actually save any space in texture memory, it is typically converted to a four-channel 32bit texture when it's sent to the card. This format really only helps save disk space.
 ----
 [[Normal Map]] [[:Category:Texturing]] [[:Category:TextureTypes]] [[:Category:Bump map]]