Scanline rendering device for generating pixel values for displaying three-dimensional graphical images

A rendering device for rendering 3-D graphical images, said rendering device coupled to a computer system, said computer system having a system processor, a database having a plurality of graphical objects, a display and a system frame buffer, said system frame buffer containing pixel shading values, said rendering device providing pixel shading values to said system frame buffer, said rendering device comprised of:

• a) A processor coupling means, said processor coupling means for coupling said rendering device to said system processor,
• b) a scanline rendering means for generating a scanline of pixel shading values from a plurality of graphical objects, said scanline rendering means including an span identifying means for identifying at least a first span of an object corresponding to a scanline being rendered, said scanline rendering means for generating each shaded pixel value of said shaded pixel values from a corresponding token, a first token including a first interpolation weight value for a first pixel, said scanline rendering means for generating a first Z-value from said first interpolation weight and Z-values of endpoints of said first span, said scanline rendering means for determining whether said first token should be converted to a null token based upon said first Z-value;
• and
• c) a scanout means for transferring a scanline of rendered pixels to said system frame buffer.

A system for rendering objects in a 3D object database, comprising:

• a) a host processor, for managing said 3D object database, for generating an activation list from said 3D object database, and for generating an active object list from said 3D object database;
• b) a bus communications circuit, being coupled in communications with said host processor, for communicating data with said host processor;
• c) a first rendering pipeline, being coupled to said bus communications circuit, for generating scanline pixel shading values responsive to receiving objects in said active object list;
• d) a horizontal interpolation circuit for identifying spans of pixels of each object in an active object list, each horizontal span being identified by a pair of end coordinates and a corresponding Z pair, said horizontal interpolation circuit for generating a plurality of pixel interpolation tokens from each horizontal span, each pixel interpolation token including a shaded color value and a weight;
• e) a hidden surface removal circuit, using said plurality of pixel interpolation tokens, for generating pixel shading values and a Z-value for each of said plurality of pixel interpolation tokens from said weight and said Z pair, said hidden surface removal circuit being coupled to a Z-buffer, said hidden surface removal circuit for converting a first pixel interpolation token to a first null token after determining that said Z-value for said first pixel interpolation token is greater than a Z-value of a corresponding pixel in said Z-buffer;
• f) a frame buffer for storing and providing pixel shading values:
• and
• g) a frame buffer communications circuit, being coupled to said first rendering pipeline and said frame buffer, for communicating said scanline pixel shading values to said frame buffer.

A rendering device for use in a computer system, said computer system having a system process, a system frame buffer and a system bus, said system bus for communicating information to and from said system processor, said rendering device comprised of:

• a) a bus attacher for coupling to said system bus;
• b) a scanline renderer coupled to said bus attacher, said scanline renderer for generating a scanline of shaded pixel values, said scanline renderer further including a first object processor for identifying a horizontal span of an object corresponding to a scanline being rendered and a Z pair for endpoints of said horizontal span, said scanline renderer being coupled to a Z-buffer, said scanline renderer for generating a pixel interpolation token for each pixel, wherein said interpolation token includes a weight, said scanline renderer for converting a first pixel interpolation token to a first null token after determining that a Z-value for said first pixel interpolation token is greater than a Z-value of a corresponding pixel in said Z-buffer, wherein said Z-value is computed using said weight and said Z pair, said scanline renderer for generating said shaded pixel values from non-null pixel interpolation tokens;
• and
• c) a system frame buffer coupler to said scanline renderer, said system frame buffer coupler for transferring said scanline of shaded pixel values to said system frame buffer.