(Historical) Hardware Support for Large Texture Maps

This page describes the (now mostly historical) challenge of supporting large textures on early hardware (roughly 1994-2008).  In the modern era of graphics cards with gigabytes of texture RAM and fast busses for instantaneous paging, is is largely a non-issue.

SGI

• High-end solution: SGI's Performer on Infinite Reality (IR)
  • Performer Guide, Chapter 12: ClipTextures (Clipmapping)
  • Introduced in Performer 2.1, a patented algorithm to allow textures that are much bigger than will fit in texture memory, and even in system memory.
  • Exploits and extends properties of MIP-maps. Efficiently pages in MIP-levels using a special hook in the Infinite Reality hardware and a high-speed bus.
  • SGI demonstrated a 32k*32k cliptexture (25m data, 800*800km) = 3 GB of memory
    • at Siggraph '98, was claiming to show a 350 GB texture database
  • Their Yosemite demo used 0.5m image data and 30M elevation data
  • was not available on SGI's Win32 platform (Cobalt)

Ways to Save Texture Memory

• Texture image depth can potentially be reduced to 16 bits
  • TGA and PNG are a common format for 16-bit textures, however.. OpenGL generally wants a 24-bit texture as input, which it will convert it to an internal format depending on what the card is capable of and what you ask for
• Texture Compression
  • Texture compression reduces the texture memory size for a texture, generally by a factor of 4x to 6x, such that it can be quickly and easily uncompressed at rendering time.
  • It also reduces the amount of on-chip bandwidth required to transfer and process the texture for rendering, which can increase fill rate.
  • It's now widely available on all 3D hardware, and it's difficult to tell the difference visually, so it's usually a no-brainer to enable compression.
  • Reportedly, "Compression is most visible with smooth multicolor gradients, and is likely to add noise to the image more often than softening it (as JPEG does).  Textures generally appear to become slightly 'busier'."

3D Card Vendors

• 
  • A normal consumer card vendor, but their cards now completely out-perform cards from the previously "high-end" 3D card market.
  • Their cards with 128 MB, and even 256 or 512 MB of RAM are becoming widespread.
  • ~110 MB of 128 is available for texturing, depending on display settings, or ~240 of 256.
• 
  • Now the leading NVidia competitor, usually in a horse race with their product releases.
  • Their top-of-the-line Radeon offering comes in 128, 256, and even greater MB

Traditional High-end PC Graphics Card Vendors

See Older/Historical Cards.

RAM requirements for a single texture, in megabytes, with and without mipmapping (MM):

size of texture	16 bit	24 bit	32 bit	16 bit w/MM	24 bit w/MM	32 bit w/MM	24 bit with 4x Compression
				(may be greater due to rounding up to meet texture memory usage constraints)
1024*1024	2	3	4	2.7	4	5.5	0.75
2048*2048	8	12	16	10.9	16	21.3	3
4096*4096	32	48	64	42.6	64	85.3	12
8192*8192	128	192	256	170.6	256	341.3	48
16384*16384	512	768	1024		1024		256

Card/Chipset Maximum Texture Size under OpenGL, Current Cards:

Chipset	Max texture RAM (MB)	Max Texture Size
NVidia GeForce series	~110/240 (128/256 on card)	4096
ATI Radeon series	~110/240 (128/256 on card)	2048