International Business Machines Corporation

Jorge Gonzalez-Lopez

Bob C Liang

Thomas P Lanzoni

Bob Cc Liang

Robert Spencer Horton

Bruce C Hempel

William L Luken, Jr

Bob Chao-Chu Liang

In a computer graphics display system, a method and processor are disclosed for drawing one of a concave polygon, self-intersecting polygon and polygon with polygonal hole. Pursuant to the method, a mask buffer organized into an M.times.N plurality of addressable constituent pixels is used. The method includes the steps of: masking the pixels of the mask buffer corresponding to the boundary of the polygon and drawing the pixels in the frame buffer of the display system corresponding to the boundary of the polygon; masking the pixels in the mask buffer corresponding to the interior of the polygon while preserving the masked pixels in the mask buffer corresponding to the polygon boundary; and drawing the pixels in the frame buffer corresponding to the interior of the polygon with reference to the masked polygon interior pixels in the mask buffer. Further processing steps include: tessellating the polygon into a set of triangles; determining the orientation of each of the triangles definitive of the decomposed polygon; and processing the pixels in the mask buffer corresponding to the interior of each triangle such that interior pixels of adjacent triangles of the same orientation are masked while interior pixels of adjacent triangles of different orientation are unmasked within the triangles' region of overlap. Specific algorithms are described for the above masking and drawing steps. In addition, a display processor implementing the described method is also provided.

Concave polygon drawing method and processor for a computer graphics

In a computer graphics display system, a method and processor are disclosed for drawing a `polygon with edge`-type primitive encountered in certain high level graphics interface programs. Both the method and processor use a mask buffer organized into a plurality of addressable constituent pixels, each pixel preferably being two bits deep. The method includes: masking the pixels in the mask buffer corresponding to the boundary to the polygon; drawing the pixels in the frame buffer of the display system corresponding to the boundary of the polygon; and drawing the pixels in the frame buffer corresponding to the interior of the polygon with reference to the content of the mask buffer. Corresponding processing steps for writing Z values in a depth buffer are also described. In addition, specific algorithms for implementing the method are set forth, along with an embodiment of a display processor implementing the method.

Method and processor for drawing `polygon with edge`-type primitives in

Z-buffer control logic that provides access AND comparison at speeds unconstrained by DRAM memory access times. A Z-buffer controller is implemented which accumulates a number of pixels in adjacent locations into an associated cell. A Z-buffer comparator accesses Z-buffer retained values for the cell in parallel, performs parallel comparisons, and passes the results to a serializer. The Z-buffer serializer returns the order of the written pixels and outputs the required values to a display interface for continued processing and display on a graphics display device.

High speed Z-buffer control

An image interpolator implements an interpolation function providing real time, continuous zoom capability to an image dispaly system. Output image pixels are obtained by interpolating the values of the color or intensity of the 2.times.2 matrix of pixels surrounding the point on the input image. The preferred embodiment employs a bi-linear interpolation algorithm implemented in the form of cascaded one-dimensional interpolation circuits. Magnification control is established so that a unit increment of the zoom controller, such as a cursor on a tablet, results in a constant increase in the degree of magnification. The coefficients required for the interpolation are generated in real time avoiding the need for time consuming table look-ups.

Image interpolator for an image display system

A lighting model processing system for a computer graphics workstation's shading function includes multiple floating point processing stages arranged and operated in pipeline. Each stage is constructed from one or more identical floating point processors. The lighting model processing system supports one or more light sources illuminating an object to be displayed, with parallel or perspective projection. Dynamic partitioning can be used to balance the computational workload among various of the processors in order to avoid a bottleneck in the pipeline. The high throughput of the pipeline system makes possible the rapid calculation and display of high quality shaded images.

Pipelined lighting model processing system for a graphics workstation's

The present invention provides for the combining of image and graphics data in a high-performance raster graphics workstation. It allows the definition of windows on the screen, the dynamic control of the position of those windows, the magnification factor (integer zoom), and a color translation table, corresponding to each window. All these functions are under user control. Response time of 10 new frame buffers generated per second provides a 'real' time response.

Image display processor for graphics workstation

Polygon vertex data is processed in three steps to create a graphics display without hidden lines and without gaps in the displayed lines. The technique permits the processing of triangles rather than polygons having four or more sides. In the first step, the Z values for the display points for the visible edges of the polygons are identified and assigned a reserved value ZCLOSE in a frame buffer. In the second step, the polygons are tessellated into triangles and the Z values for the display points on the triangles are computed and each depth buffer storage location is updated so as to contain the value of points closest to the viewpoint while the frame buffer is written with a background color. In the final step, the Z values for the display points of the polygon edges are again computed and compared with the corresponding Z values in the depth buffer. The depth buffer is updated with the computed values if the stored value is equal to ZCLOSE or if the computed value represents a position closer to the viewpoint than the stored value and the frame buffer is then written with a foreground color for the display point in question.

Hidden line removal method with modified depth buffer

Method and apparatus for providing interpolated display characteristic values, such as intensity or Z value, for pels within a polygon to be displayed by a computer graphics display system. A scanning sequence generates pel addresses such that each pel address so generated is contiguous with a previously generated pel address. The parametric value rate of change in both the X and the Y direction is determined, and expressed as an integer value and a remainder quantity. The remainder quantity is used to determine a sequence, driven by pel address changes, by which the integer parametric value increment from pel to pel is incremented or decremented by one in a regular sequence that assures that the error in the computed parametric value for each pel never exceeds 0.5 parametric value units.

Growing community of inventors

Red Hook, NY, United States of America

Jorge Gonzalez-Lopez