Pixar Image Computer

Creation When George Lucas recruited people from NYIT in 1979 to start Lucasfilm's Computer Division, the group was set to develop digital optical printing, digital audio, digital non-linear editing and computer graphics. The machine sold for $135,000, but also required a $35,000 workstation from Sun Microsystems or Silicon Graphics (in total, ). The original machine was well ahead of its time and generated many single sales, for labs and research. In an attempt to gain a foothold in the medical market, Pixar donated ten machines to leading hospitals and sent marketing people to doctors' conventions. However, this had little effect on sales, despite the machine's ability to render CAT scan data in 3D. Pixar did get a contract with the manufacturer of CAT Scanners, which sold 30 machines. By 1988, Pixar had only sold 120 Pixar Image Computers. a high performance bus, a hardware image decompression card, 4 processors (called Chaps or channel processors), very large memory cards (VME sized card full of memory), high resolutions video cards with 10-bit DACs which were programmable for a variety of frame rates and resolutions, and finally an overlay board which ran NeWS, as well as the 9-slot chassis. A full-up system was quite expensive, as the 3 GiB RAID was $300,000 alone. At this time in history, most file systems could only address 2 GiB of disk space. This system was aimed at high-end government imaging applications, which were done by dedicated systems produced by the aerospace industry and which cost a million dollars a seat. The PII-9 and the associated software became the prototype of the next generation of commercial "low cost" workstations. Demise and legacy In 1990, the Pixar Image Computer was defining the "state of the art" in commercial image processing. The Pixar computer business was sold to Vicom Systems in 1990 for $2,000,000. Vicom Systems filed for Chapter 11 within a year afterwards. Many of the lessons learned from the Pixar Image Computer made it into the Low Cost Workstation (LCWS) and Commercial Analyst Workstation (CAWS) program guidelines in the early and mid-1990s. The government mass deployment that drove the PII-9 development occurred in the late 1990s, in a program called Integrated Exploitation Capability (IEC). == Design ==

The P-II could have two Channel Processors, or Chaps. The chassis could hold 4 cards. The PII-9 could hold 9 cards (4 Chaps, 2 video processors, 2 Off-Screen Memory (OSM) cards, and an Overlay Board for the NeWS windowing system). NeWS was extended to control the image pipeline for roaming, image comparison, and stereo image viewing. Each Chap is a 4-way parallel (RGBA) image computer. This was a SIMD architecture, which was good for imagery and video applications. It processed four image channels in parallel, one for red, one for green, one for blue, and one for the alpha channel (whose inventors have connections to Pixar). The Chaps did 16-bit integer arithmetic. The memory for images only stored 12 bits per color channel (or 48 bits per pixel). 4 bits of extra precision were added to the end when loaded into the Chaps. A Unix host machine was generally needed to operate it (to provide a keyboard and mouse for user input). The system could communicate image data externally over an 80M per second "Yapbus" or a 2M per second multibus to other hosts, data sources, or disks, and had a performance measured equivalent to 200 VUPS, or 200 times the speed of a VAX-11/780. == PXR File Format ==

Pixar Image Computer uses the 'Pixar storage standard' PXR File format. PXR file have structure: 1. Header (512 bytes) 2. Tile pointer table (8 × numberTiles bytes) 3. Picture data Origin of image is left top corner. All data in file use small-endian byte order. Header (512 bytes) Tile pointer table (8 × numberTiles bytes) The tile pointer table starts at byte 512 from the start of the file and has 1+ tile pointers. To calculate the number of tiles for x direction: 1 + (pictureWidth − 1)/tileWidth and y direction: 1 + (pictureHeight − 1)/tileHeight Tile order is sweep from left to right, from top to bottom; first tile 0 is at left top of picture and last tile (totalNumberTiles − 1) is at right bottom of image. Dumped & Encoded Pixel Data Picture storage (at 2 bytes at byte 426 from start of file) can have values: 1. 0 - 8-bit channels encoded 2. 1 - 12-bit channels encoded 3. 2 - 8-bit channels dumped 4. 3 - 12-bit channels dumped Dumped tiles store pixel data direct with order RGBA (4 channels), RGB (3 channels), or R (1 channel, grey image) for whole tile and no have extra byte or mark show end of scan line. Encoded tiles use packets for store image data. Each packet have 2 byte header and encoded pixel data after. Two byte header have flag and count for packet, flag is 4 low bits of byte 2, count is top 4 bits of byte 2 (top bits) combine with 8 bits of byte 1 (low bits) create 12 bit count. Flag have values: For flag value 1 and 3, count is p - 1 number of pixels dumped in packet. For flag value 2 and 4, count is n - 1 number of run lengths in packet, λ is 1 byte (8 bits) store p - 1 number times repeat same pixel. Flag value 3 and 4 only use one A value for that packet and store only RGBA (4 channels) data. One packet never store pixel data from different scan lines but each scan line can use different/any flag. Pixar 12 bit pixel format Pixar Image Computer and PXR use special 12 bit fix point format have range [-1.5; 2.5), with 10 bits of precision (the documentation describes the range as [-0.5; 1.5) plus an "overflow bit"). 16-bit coefficient values Pixar Image Computer also has special 16-bit fixed-point data type (for mảtix value, etc.) have name 'coefficient' with range [-2.0; 2.0) and 14 bits of precision. == Use ==

In the early 1990s, the Pixar Computer was used for medical imaging, including MRI and CT scans at Georgetown University Walt Disney Feature Animation, whose parent company later purchased Pixar in 2006, used dozens of the Pixar Image Computers for their Computer Animation Production System (CAPS) and was using them in production up through Pocahontas in 1995. == References ==