InfiniteReality

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InfiniteReality

• A Real-Time Graphics System

By Montrym, Baum, Dignam and Migdal
Presented by Alexander Stevenson
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Introduction

• System Goals (applications)
• Features
• History

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Introduction System Goals

• Render LOTS of lighted, smooth shaded, depth
  buffered, texture mapped, antialiased triangles.
• Allow complex visual simulations, with constant
  update rates of 60Hz .
• Integrate well with different host platforms
  (Onyx and Onyx2)

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Introduction Features

• First high-end SGI system to natively support
  OpenGL.
• Support for virtual texture memory (through
  clip-mapping and DMA texture loading/paging)
• Scene load management
• Configurable Video Output

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Introduction History

• InfiniteReality was introduced in 1997
• This was the same time as Pentium IIs, the G3,
  and
• The 3Dfx Voodoo 1?!?!?!
• "Pure3D's 4MB of texture memory and TV-out
  capabilities add a new twist to our technology
  that PC gamers are sure to enjoy. 3Dfx, August
  25, 1997

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Architecture

• Three parts
• Geometry
• Host interface, 4 Geometry Processors
• Raster Memory
• Fragment generator, 80 image engines
• Display Generator
• Drive up to 8 output channels, each with own
  video timing, gamma correction

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Architecture
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Features

• Virtual Textures
• Clip-maps
• Loading and Paging
• Scene Load Management
• Video Configurability

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Virtual Textures

• Virtual Textures are textures too large to fit
  in physical texture memory
• Instead they are stored in system RAM, and
  accessed using DMA
• Previous methods required breaking up large
  textures into small pieces
• 1 piece per fragment
• Clip-maps are used to get around this

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Virtual Textures Clip-Maps

• If screen resolution is 1024x768, we cant see
  more than 1024x768 pixels of texture at one time
• We can use this to our advantage

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Virtual Textures Clip-Maps

• Weve all seen mip-maps
• A clip-map is like a subset of a mip-map,
  centered on where the user is looking in a
  texture
• (Keep in mind that we cant see more than 1
  framebuffer worth of any texture at a time)

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Virtual Textures Clip-Maps

• Because the clip-map contains only a portion of
  the texture, it needs to be updated as the
  viewers position changes
• InfiniteReality does this intelligently so that
  we dont need to replace all the data each time
  we recalculate the clip-map
• This method allows scenes to be drawn as though
  the entire mip-map was resident in texture memory

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Virtual Textures Clip-Maps
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Virtual Textures Clip-Maps

• Clip-maps require much less memory than mip-maps
  to store
• Also, InfiniteReality is clever enough to use the
  best detail level available, if for some reason
  the clip-map of the desired area isnt available
  in the desired quality.

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Virtual Textures Loading and Paging

• Loading and paging is minimized by native support
  for OpenGL texture formats.
• Geometry system does pixel unpacking and format
  conversion
• DMA hardware handles stride and address
  arithmetic

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Features

• Virtual Textures
• Scene Load Management
• Pipeline Performance Statistics
• Dynamic Video Resizing
• Video Configurability

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Pipeline Performance Statistics

• We want to keep frame rates high.
• System provides a mechanism for detecting
  Geometry-Raster stalls, as well as stalls in
  upstream Geometry path.
• This allows us to detect fill-limited or
  geometry-limited scenes, respectively.
• The application can then reduce the complexity of
  a scene as necessary, to avoid geometry
  bottlenecks.

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Dynamic Video Resizing

• What do we do for fill-limited scenes?
• Each frame, fill requirements are analysed.
• If necessary, frames can be drawn at a lower
  resolution, and then digitally scaled up by the
  video hardware.
• In practice, we can often reduce the resolution
  up to 25 in each dimension, without
  substantially degrading the image quality.

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Features

• Virtual Textures
• Scene Load Management
• Video Configurability

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Video Configurability

• Anyone who has done stereo or multiple monitors
  on the Onyx has used ircombine
• This allows a user to dynamically select
  different formats, sections of framebuffer, pixel
  depth, pixel size, and other attributes for each
  video output.
• To see this in action, check out FSC 23??

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Performance

• Infinite Reality was really good at the time.
• IR 11.3 million triangles per second
• Voodoo 3 million triangles per second
• Now, NVIDIA GeForce 2 Ultra does
• 31 million triangles per second

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Performance

• Dont let the numbers fool you InfiniteReality
  wasnt built to draw unlit, untextured triangles.
• Designers put a lot of effort into optimizing for
  OpenGL mode switches, and support for large
  textures, and InfiniteReality may well win out in
  cases that use these.

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Conclusion

• In the room with 1 Onyx, and 4 Linux based
  GeForce 2 machines, few even know the Onyx is
  there. Nobody is asking to use it.
• With graphics accelerators improving so rapidly,
  expensive SGI workstations provide less
  bang-for-the-buck.
• For VR (which needs stereo), or CAVEs (which need
  multiple displays), InfiniteReality is still king.

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The End