International Business Machines Corporation

Joe Christopher St Clair

Mark Ernest Van Nostrand

Russell S Cook

A sphere mode texture coordinate generator circuit for use in a graphics adapter of a data processing system is disclosed. The circuit includes a set of input multiplexers configured to receive x, y, and z components of a normal vector and a unit vector corresponding to the current vertex. The circuit further includes a set of functional units such as a floating point multiplier, a floating point adder, a floating point compare-to-zero unit, and an inverse square unit. The functional units are configured to receive outputs from the set of multiplexer and are enabled to perform floating point operations on the outputs of the set of multiplexers. A controller or state machine of the circuit is enabled to determine the state of select inputs to each of the set of multiplexers. The controller manages the multiplexer select inputs such that the circuit determines sphere mode texture coordinates in response to receiving the normal vector and the unit vector. The circuit typically includes a set of latches, where the input of each of the latches is connected to an output of a corresponding input multiplexer. The circuit may include an S Out multiplexer and a T Out multiplexer, where the output of S Out multiplexer represents the S sphere mode texture coordinate and the output of the T Out multiplexer represents the T sphere mode texture coordinate calculated in compliance with a predetermined specification such as the OpenGL&reg; specification.

Sphere mode texture coordinate generator

A method and apparatus in a geometry engine having a plurality of stages for processing graphics data. An immediate mode data stream is received at a first stage within the plurality of stages. Data from the immediate mode data stream is stored in a storage to build a vertex data structure for processing within the plurality of stages. The vertex data structure is transmitted to the first stage for processing in response to receiving a signal to transmit the vertex data structure. Data for the vertex data structure remains in the storage as default data for a subsequent vertex data structure.

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Round Rock, TX, United States of America

Joe Christopher St Clair