Darwyn Peachey
Abstract:
Texture On Demand (TOD) is a technique for organizing large amounts of
stored texture data in disk files and accessing it efficiently. Simply
reading entire texture images into memory is not a good solution for
real memory systems or for virtual memory systems. Texture data should be
read from disk files only on demand. In the TOD technique, each texture
image is stored as a sequence of fixed-size rectangular regions called
tiles, rather than in the conventional raster scanline order. Tiles are
an appropriate unit of texture data to read into memory on demand. As
fixed-size units with good locality of reference in a variety of rendering
schemes, tiles can be cached in main memory using the paging algorithms
common in virtual memory systems. Good results have been obtained using
an LRU tile replacement algorithm to select a tile to be deleted
when main memory space is required.
Prefiltered textures are an important means of limiting bandwidth. TOD
uses a set of prefiltered texture images called an r-set, a generalization
of the texture pyramid (mip map). Texture filtering methods are reconsidered
in terms of their performance in the TOD environment. Efficient filtering
methods using the r-set are described.
The paper describes various implementations of TOD, including a virtual
memory implementation and a distributed implementation on a 16-processor
multicomputer.
Paper (PDF)
Available as Pixar Technical Memo #217