Apparatus for converting pyramidal texture coordinates into corresponding physical texture memory addresses

A display apparatus comprising a host processor with associated main memory for the storage of object primitive data and texture definitions and a display processor with associated display memory and texture memory, the host processor comprising:

• means for storing in the texture memory at least one pyramidal array of texel values, said pyramidal array comprising a plurality of two-dimensional (2-D) arrays of texel values representing a given 2-D modulation pattern at at least two levels of resolution defined by respective values of a level coordinate;
• and
• means for supplying object primitive data to the display processor, including an indication that a pattern of modulation is to be applied to the object primitive in accordance with texel values stored in the pyramidal array in the texture memory;
• the display processor comprising:
• means for generating from the object primitive data a series of pixel addresses for application to the display memory and a corresponding series of 2-D texture coordinate pairs each with an associated level coordinate, to effect a mapping of the stored texel values representing a pattern or modulation on to the object primitive at a level or levels of resolution defined by the associated level coordinate;
• and
• means for receiving each 2-D texture coordinate pair and associated level coordinate and for generating therefrom a physical texture memory address for application to the texture memory;
• wherein the texture memory comprises a linearly addressed (one-dimensional) texture memory, the means for storing the pyramidal array of texel values comprises means for storing each 2-D array in linear form in the texture memory and means for generating page location information for locating each such array in the texture memory, and the means for generating the physical texture memory address comprises:
• a converter circuit for converting pyramidal texture coordinates into corresponding linear (one-dimensional) physical texture memory addresses in an electronic display apparatus, said converter circuit comprising:
• a pyramidal coordinate input for receiving a two-dimensional (2-D) texture coordinate pair and an associated level coordinate;
• and
• means for generating, from the received coordinate pair and level coordinate, a corresponding linear (one-dimensional) physical texture memory address;
• wherein the means for generating the linear/one-dimensional) physical texture memory address comprises:
• means for generating, from the received level coordinate, page location information locating a corresponding array of texel values in a linear address space, said page location information including information defining a linear base address and a width value for the corresponding array;
• and
• a texture address converter comprising offset generating means for combining the 2-D texture coordinate pair with the width value and the level coordinate to generate a linear offset address, linear address generating means for combining the base address with the generated linear offset address to generate a linear physical texture memory address for application to a linearly-addressed texture memory, and means for generating n further physical addresses to form a group of n+I physical addresses all corresponding to the same level coordinate but with 2-D texture coordinate pairs offset from the received coordinate pair so as to allow parallel addressing of a patch of n+1 texel values in a stored array.