Packing Square Tiles into One Texture

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Packing Square Tiles into One Texture
Philippe Decaudin Fabrice Neyret
GRAVIR/IMAG-INRIA, Grenoble, France
?

• Eurographics 2004

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Introduction

• Aim
• Pack square texture tiles of the same size into 1
  texture
• Reduce space loss

10tiles

• Packing is important
• Graphic context switching ? performance penalty
• Easier to manage one texture instead of a set

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Introduction (cont.)

• Why packing N tiles with no space loss is
  difficult ?
• Texture size is constrained
• w / h 2 i ? w and h are bounded (lt 4096)

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Packing an arbitrary number of tiles

• Space loss can be substantial
• E.g., packing 5 tiles

37 unused
55 unused

• Best known packings
• Jennings95, Fridman98
• Complex schemes
• And still space lost

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Our packing scheme

• We propose a packing scheme with no loss for many
  N
• Ranges of uncovered numbers are small? loss
  greatly reduced for other values of N

• The trick texture space has special properties
• Torus topology ? texture addresses wrap
  (GL_REPEAT or
  D3DADDRESS_WRAP)
• Can be rotated

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Basic example
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? 2, ? 2n and ? n2 packing schemes

• ? 2n scheme ?
  ? n2 scheme ? ? 2 scheme

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Generalization

• We can define ? (n2 k2)
• First, let consider the packing of 5 tiles (22
  12)

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The ? (n2 k2) packing scheme, with k ? n

• n ? n square subdivided by 2 sets of parallel
  slanted lines

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Reachable numbers

• ? (n2 k2) schemes provide a dense set of
  reachable N with no loss

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Conclusion

• We have shown that N tiles can be packed into 1
  texture with no space loss for all N of the
  form

• Allows many more possible schemes for no loss
  packing than the common schemes

• For an arbitrary N, it provides a packing with
  little loss

• Could be extended to 3D textures for cubic
  tilesspace saved for volume data could be
  consequentialKraus-Ertl02, Lefebvre-Neyret03

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Thanks
Questions ?

• http//www-imagis.imag.fr/Publications/2004/DN04b

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Reachable numbers (cont.)

• Similarities with prime factor decomposition,
  with some gaps.Some primes missing 3, 7, 11,
  19, 23,