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# 09_Dxt 압축 알고리즘 소개

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### 09_Dxt 압축 알고리즘 소개

1. 1. DXT (http://gamecode.org) 2009.10.11
2. 2. DXT• – – –• –• – DDS – Nvidia – DirectX (DirectX Texture Tool) – ATI compressonator• . DXT1, DXT3, DXT5
3. 3. DXT ?• – – ,• – : Allegorithmic "Substance Air“ • a new genetation of texture • http://www.allegorithmic.com • ~ –• DXT ~
4. 4. DXT• 4x4 – read 16 – Bilinear Filtering – – (cache hit!!)• – dxt1 4x4 8 – 16 2*16 => 32 (1/4 ) (X8R8G8B8 1/8 )• – ( ) – ( ) –• !!
5. 5. DXT1 기본 알고리즘(1)• 4x4 – 8 – 2 +2 +4 – 16 + 16 + 32 – 16 + 16 + (2 +2 + ... + 2 ) – RGB1(565:16) + RGB2(565:16) + T00(2) + T01(2) + T02(2) + T03(2) + T10(2) + T12(2) + .. + T33(2)• PCA ( ) – (Eigen Vector) – = ( )
6. 6. DXT1 기본 알고리즘(2)• 16 – PCA – 3 (RGB)• –• – RangeFit – ClusterFit – – 참고 : http:/ / code.google.com/ p/ libsquish/
7. 7. DXT1 기본 알고리즘(3)• Pseudo Code ??? (0, 1 RGB0,RGB1 )• – RGB0 >= RGB1 – DXT1 BLACK 0
8. 8. DXT3/ DX5 알고리즘(1)• DXT 3 – RGB DXT1 – 16 4 (8 )• DXT5 – (RGB ) – 8 • 1 +1 +6 • 8Bit + 8Bit + 3Bit + 3bit ... + 3Bit • ALPHA0(8) + ALPHA1(8) + T00(3) + T01(3) + .. + T32(3) + T33(3) • RGB (8 ) – Pseudo Code
9. 9. DXT3/ DX5 알고리즘(2)– RGB BLACK 0, 255 • ALPHA1 ALPHA0 8 6+2– Pseudo Code
10. 10. • ( ) – ( )• – • • HALO – DXT5 , RGB , –• DXT – : 16 DXT• (Official) – http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt