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Binary Compression Rates for ASCII Formats

Binary Compression Rates for ASCII Formats. Martin Isenburg Jack Snoeyink University of North Carolina at Chapel Hill. Take this home:. “We can store compressed geometry as ASCII and achieve benchmark compression rates.”. “Geometry compression does not require binary.”.

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Binary Compression Rates for ASCII Formats

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  1. Binary Compression RatesforASCII Formats Martin Isenburg Jack Snoeyink University of North Carolina at Chapel Hill

  2. Take this home: “We can store compressed geometry as ASCIIand achieve benchmarkcompression rates.” “Geometry compressiondoes not require binary.” “This enables full conformancebetween ASCII and binary X3D.”

  3. Overview • Motivation • Benchmark Compressor • Storing Bits as ASCII • Results • More Motivation • Demo • Summary

  4. Motivation

  5. Why ASCII Scenes? • authors like text-based 3D • wide acceptance • read, understand, modify, and save scene with any text editor • Web3D Developer survey: “very important” • no binary standard • rather readable ASCII than binary

  6. Why Compression? • authors want compressed 3D • smaller files • faster download • Web3D Developer survey: “very important” • data-heavy nodes • audio / images / video • geometry

  7. Approaches to Compression • binary formats: • proprietary compression schemes • automatically “protects” the content • Shockwave3D, Viewpoint, Virtue3D, Cult3D ... • gzipped text-based formats: • human readable ASCII content • WRL, X3D, OBJ, PLY, SMF, OFF…

  8. Compression Standards • software to read, edit, and write content is available and widely used • binary compression standards: • audio data: MP3 • image data: JPEG, GIF • movie data: MPEG • geometry data: ?

  9. Why no Standard yet? (1)  structure of 3D data is complex • audio: sequence of numbers • image: block of numbers • video: sequence of blocks of numbers • geometry: vertex positions + triangles (or polygons ?)+ texcoords (1, 2, 4, 8 layers ?)+ normals (smoothing groups ?)+ colors (per-face ? per-vertex ?)+ bones (1, 2, 3 attachments ?)

  10. my mom, dad, sister,aunt, uncle, grandma,friends, neighbors, … gamers, researchers Why no Standard yet? (2)  3D data is much less used • audio: everybody • image: everybody • video: everybody • geometry: anybody ?  3D data is not a consumable product on its own  profitability issues

  11. Geometry compression & X3D • long wanted feature (`96) • compression requires binary VRML • Compressed Binary Format workgroup • binary VRML + 5 new compressed nodes • but … CBF proposal refused (`98) • problem-child: the binary specification • second call for BF proposals (`00) • unanswered

  12. Compression without Binary  Web3D 2002 paper • eliminate binary requirement • only requires specification changes where it matters • does not interfere with how authors publish content • does not affect (overall) readability Coding Polygon Meshes as Compressable ASCII [Isenburg & Snoeyink, 02]

  13. Design Objective • work with Shout3D API • pure Java viewer (plugin-less) • fast, light-weight decoding • low computational complexity • small size for decoder class • be worthwhile less than 400lines of code 5,381 bytes 1 : 6

  14. ASCII coder binary coder • How good is the compression? • compare to benchmark coder • oops … • New Design Objective:>>> Maximum Compression <<< • produce ASCII output • compress with “gzip -9” • be as good as benchmark

  15. BenchmarkCompressor

  16. Benchmark Compressor • Connectivity Coder • codes connectivity as sequence of vertex degrees Triangle Mesh Compression [Touma & Gotsman, 98] • Geometry Coder • codes geometry as sequence of corrective vectors  only handles fully triangulated meshes  no support for texture coordinates

  17. Compressing Polygon Mesh Connectivity withDegree Duality Prediction [Isenburg, 02] Compressing Polygon Mesh Geometry withParallelogram Prediction [Isenburg & Alliez, 02] handling textured meshes: Compressing the Property Mapping of Polygon Meshes [Isenburg & Snoeyink, 01] Compressing Texture Coordinates with Selective Linear Predictions [Isenburg & Snoeyink, 03] Polygon Mesh Compressor handling non-triangular meshes:

  18. It’s available! • a working Webimplementation • Java applet • based on node set of Shout3D • WRL,OBJ,PLY,OFF,SMF,… • compress anymodel online

  19. [results from Web3D’02 paper] 66.2 29.4 34.9 40.9 39.9 34.6 Binary vs. ASCII binary difference ASCII scene lion wolf raptor … horse cat dog average 42.6 18.4 21.5 20.3 22.5 21.5 55 % 60 % 62 % 101 % 77 % 61 % 74 %

  20. Mesh Compression Process grow region + store symbols

  21. Why is binary so much better? Because it … • is binary? • stores symbols in binary? • uses better predictiveencoding scheme? • compresses symbols withentropy coding? • allows to store a bit-stream? No! Not quite! Sort of. Yes, but … Yes!

  22. 0.2 bits 1.3 bits 2.0 bits Entropy Coders for a symbol sequence of t types t 1  Entropy = pi• log2( ) bits pi i =1 # of type t pi= # total

  23. Contents of Binary File • an array of bits [0 0 1 1 0 1 0 0 1 1 1 1 0 … 1 0 0 0 1 0 1 0] • six floats xmin= -1.2323 ymin= -2.1324 zmin= -1.7123 xmax= 2.6731 ymax= 0.8372 zmax= 3.4971 • an integer precision = 12

  24. triceratops.wrl Shape {appearance Appearance {material Material {diffuseColor1 .5 0 }}geometry IndexedFaceSet { creaseAngle 0.9 coord Coordinate { point [-0.0715 1.7609 ... -0.4479 -1.5153 1.5304] } coordIndex [7 6 209 204 -1 4 … 4577 4223 4222 -1]} }

  25. triceratops_compressed.wrl Shape {appearance Appearance {material Material {diffuseColor1 .5 0 }}geometry CompressedIndexedFaceSet { creaseAngle 0.9 code [ 0 0 1 1 1 0 1 1 0 1 1 1 0 1 1 0 1 1 1 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 1 0 … 1 0 0 0 1 1 1 0 1 1 0 1 1 0 1 1 0] bits 12 box [ -1.2323-2.1324 -1.7123 2.67310.83723.4971]} }

  26. triceratops_compressed.wrl Shape {appearance Appearance {material Material {diffuseColor1 .5 0 }}geometry CompressedIndexedFaceSet { creaseAngle 0.9 code “AQg+N9gOd+Rhh+lXdfzKEyz0CCZUJHLs3+ fWpsTQFxortsk8XW8j7jEZwL … vXS7GVbHHUuX” bits 12 box [ -1.2323-2.1324 -1.7123 2.67310.83723.4971]} }

  27. Storing Bitsas ASCII

  28. Design Goals • resulting ASCII should be “safe” obvious choices: • uuencode • base64 • Hexbin • represent binary files with a set of 64 ASCII characters • other possibilities: 2 …. 96 chars

  29. LT[6] LT[19] … Design Goals • resulting ASCII should be “safe” • conversion should be simple efficient implementation byusing 2k ASCII characters • value of k bits • look-up table LT = {‘A’,‘B’,‘C’,‘D’,‘E’,‘F’,‘G’,‘H’, ……,‘+’,‘=’} [0 0 1 1 0 1 0 0 1 1 1 1 0 1 … ]

  30. number of ASCII chars expansion factor: 8 / log2(n) Design Goals • resulting ASCII should be “safe” • conversion should be simple • ASCII representation should be compact • 32 chars = 60.0 % • 64 chars = 33.0 % • 96 chars = 21.5 %

  31. Design Goals • resulting ASCII should be “safe” • conversion should be simple • ASCII representation should be compact • size of ASCII representation of bits after “gzipping” should be close to original

  32. Results

  33. fish.wrl Shape {appearance Appearance { material Material { modulateTextureWithDiffuse truediffuseColor1 1 1 } texture ImageTexture { url fish.jpg }}geometry IndexedFaceSet { creaseAngle 0.9 coord Coordinate { point [-0.0715 4.7609 6.3930 ... -0.4479 -4.5153 4.5304] } coordIndex [ 7 6 209 204 -1 4 217 … 4577 -1 4577 4223 4222 -1 ] texCoord TextureCoordinate { point [ 0.3735 0.9441 0.3289 … 0.2666 0.4990 0.1082 ] } texCoordIndex [ 0 1 2 3 -1 4 5 6 7 … 4311 -1 4311 4293 4683 -1 ]} }

  34. fish_compressed.wrl Shape {appearance Appearance { material Material { modulateTextureWithDiffuse truediffuseColor1 1 1 } texture ImageTexture { url fish.jpg }}geometry CompressedIndexedFaceSet { creaseAngle 0.9 code “AQg+N9gOd+Rhh+lXdfzK20Eyz0CCZUJHMK8EKLs3QrP+ fWpsTQFxo4dPVVZ0pGK720hVQw3a9xXrtsk8XW4d8j7jEDfP7pC hVQw3a9xXrtPTsk8XW8j7jEDfP7pCgEofTPoTnfUYfTWzzAbc9eh Fji6UL0ZwL … vXS7GVbHHUuX“ bits 12 box [ -1.9725 -7.6861 -10 1.9725 7.6861 10 ] bits_tex 10 box_tex [ 0.0146 0.0749 0.9896 0.9834 ]} }

  35. resulting file sizes [without gzipping the text file] IFS ratio comp IFS scene lion wolf raptor … horse cat dog average 1,360 569 586 749 791 586 57 25 29 27 30 29 1 : 24 1 : 23 1 : 20 1 : 28 1 : 26 1 : 20 1 : 25

  36. resulting file sizes [with gzipping the text file] IFS ratio comp IFS scene lion wolf raptor … horse cat dog average 442 183 200 266 267 186 43 19 22 21 23 22 1 : 10 1 : 10 1 : 9 1 : 13 1 : 11 1 : 8 1 : 11

  37. Binary vs. ASCII binary difference ASCII scene lion42.6 43.2 1.3 % wolf 18.4 18.7 1.8 % raptor 21.5 21.9 1.7 % … horse 20.3 20.6 1.7 % cat 22.5 22.8 1.6 % dog 21.5 21.9 1.7 % average 1.7 %

  38. MoreMotivation

  39. Scene.x3d .gz .gz “living room” “living room” IFS IFS ? “frame” “frame” compress T IFS T IFS “mona lisa” “mona lisa” IMG 12 bits IMG “statue” “statue” T IFS T CIFS asc2bin asc2bin bin2asc bin2asc Scene.bx3d Scene.bx3d “living room” “living room” IFS IFS “frame” “frame” compress T IFS T IFS “mona lisa” “mona lisa” IMG 12 bits IMG “statue” “statue” T IFS T CIFS ASCII binary Compression Scene.x3d ASCII binary

  40. Complete Conformance • compressed nodes exist in ASCII and binary • going back and forth between the two is a very simple mapping • same decompression algorithm used – no matter if compressed node stored in ASCII or binary

  41. Demo > localweb <

  42. Summary

  43. two alternativerepresentations author’s decisionat publishing time Summary (1) • completely independent things: • ASCII format • binary format • use of compressed geometry nodes • store compressed nodes in ASCII • as compact as if stored in binary (after gzipping)

  44. Summary (2) • provide “bit-field” in ASCII formats • same decompression algorithm for ASCII and binary version • full conformance between ASCII and binary version of X3D --- --- including compressed nodes  design/decide compression now without waiting for a binary format !!!

  45. Thank you.

  46. Example XML node CompressedIndexedFaceSet : IndexedFaceSet{ MFbyte [out] code NULL IC SFint32 [out] bit [1..24] IC SFint32 [out] bit_tex [1..16] ICSFint32 [out] bit_col [1..16] IC SFint32 [out] bit_nor [1..16] IC SFvec6f [out] box [1..24] IC SFvec4f [out] box_tex [0 0 1 1] ICSFvec6f [out] box_col [0 0 0 1 1 1] IC SFbool [] valid [false] IC }

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