Abstract: A method and apparatus for accessing a cache memory of a computer graphics system, the apparatus including a frame buffer memory having a graphics memory for storing pixel data for ultimate supply to a video display device, a read cache memory for storing data received from the graphics memory, and a write cache memory for storing data received externally of the frame buffer and data that is to be written into the graphics memory. Also included is a frame buffer controller for controlling access to the graphics memory and read and write cache memories. The frame buffer controller includes a cache first in, first out (FIFO) memory pipeline for temporarily storing pixel data prior to supply thereof to the cache memories.

Abstract: A method for anticipation and tracking eye movement for head tracked projectors which divides a projection surface into spherical triangles and uses interpolating calibration values stored at each vertex of the triangle. A calibration map is used that contains information about the relationship between the user's head orientation and where they are looking with their eyes at each calibration point. The projection surface is divided into spherical triangles which are searched to find the triangle which contain the user's interpolated view point by performing a dot product test between the interpolated view point and the unit normal vectors inside the three planes that make up the sides of the spherical triangle extended back to the eye point. When a dot product test fails for any side of the triangle the pointer is followed to the adjacent triangle where the test starts over.

Abstract: A method for creating a span-based multisample Z-buffer pixel processor in a computer graphics system to thereby reduce a quantity of data that must be stored for each pixel in a frame buffer thereof. By taking advantage of areal coherence, the quantity of data that must be stored in each pixel is reduced. By employing merging, the method is also able to ensure than pixel storage requirements do not grow beyond a predetermined limit.

Abstract: This invention relates generally to the field of computer graphics display, and more particularly to reducing the amount of time needed to render complex virtual scenes on a computer graphics display. This invention combines the advantages of the prior art methods of list priority and depth buffering (e.g. Z-buffering) with new simplified and enhanced full buffer processes. In one embodiment, a simplified full buffer arrangement enables the elimination of rendering primitives prior to pixel shading for regions of the screen which have previously been covered by closer primitives. Another embodiment provides for an enhanced full buffer that combines the coverage of a previously rendered primitive in a partial buffer and associates it with a current primitive to cover pixel arrays.

Abstract: A geometric processor provides object primitives, as triangles, in graphic display image space to support a dynamic display. The image space is defined by pixels, in turn specified in arrays as spans. In a multi-level scanning operation, primitives are scanned at a first level to locate lapped spans that are lapped by primitives. At a second level, spans are scanned to process pixels that are lapped by primitives. An alternative embodiment discloses three-level scanning in association with parallel pixel processing. Concurrent texturing structure operates along with cache memories.

Abstract: A method for rendering large-area time-based shadows. A first step is to pre-process a database of three dimensional constructs that define all primitives and attributes of the primitives in a three dimensional simulated environment. The pre-processing step determines the time relevant behavior of the shadows by calculating an angle at which the primitive is illuminated, and an angle at which illumination ceases. The second step is to process the database at run-time using the pre-processed database of three dimensional constructs and pre-calculated illumination and no-illumination angles.

Abstract: A method and apparatus for rendering a real-time synthetic environment on a computer display. A hidden surface removal technique is provided which combines an efficient pixel rendering architecture with a simplified modeling process. Specifically, the computer pixel graphics hardware processing load is balanced against a software geometric load to obtain optimum rendering performance by utilizing a "full" buffer in combination with adaptations of the z-Buffer and priority-list algorithms.

Abstract: A new method and apparatus for creating, positioning and manipulating a garbage matte which obscures everything outside of a three-dimensional physical set or blue stage. Effectively, the garbage matte is a "negative" of a blue stage. What is important is that the garbage matte is created either as a virtual enclosure around all virtual objects in the virtual environment, or simply as a background color of the graphics engine generating the garbage matte. In this way, the garbage matte provides extensions of blue screens which comprise the blue stage, extending all the way around and behind the television cameras. Consequently, a compositor will not include in a composited output image those physical set elements which are masked by the virtual garbage matte. The compositor will replace areas hidden by the garbage matte with image data supplied by the computer image generator which stores the virtual environment.

Abstract: A method and apparatus for producing data in a virtual set memory representing a composite image. The composite image data is produced from a combination of data representing a virtual image and data representing a camera field of view image. The invention includes a plurality of cameras, each disposed for developing data representing a respective field of view and each having a still store frame buffer associated therewith for receiving and storing data representing virtual images. The still store frame buffers are configured for subsequent selective retrieval. The invention also includes a virtual image data source for generating data representing virtual images and for supplying such data to the still store frame buffers associated with each of the plurality of cameras.

Abstract: A patient-interactive method and apparatus for measuring eye refraction includes a display for producing, alternately, two spaced-apart light spots, and an aperture device for passing light from one spot through an aperture in one position, to travel to the eye, and for passing light from the other spot through an aperture in a second position, to travel to the eye. If the patient sees a single spot, the eye is properly refracting, but if he/she sees two spots, the eye is not properly refracting. Apparatus is provided to allow the patient to adjust the spacing of the light spots, and thus the angle that light enters the eye, until the patient views a single light spot. The amount of adjustment of the spacing of light spots is measured to thereby provide a measure of diopter correction necessary to correct the refraction error.

Abstract: A method and apparatus for performing a lens calibration procedure which is executed for each camera and lens pair. The calibration procedure is performed to determine the camera and lens nodal point offset and field of view, plus image offset in both the horizontal and vertical directions as a function of lens zoom and focus settings. The method includes the step of providing apparatus which enables the semi-automatic and rapid entry of data points representing lens zoom and focus setting information, thereby eliminating a source of human error. The general method includes the steps of creating a real environment and an identical virtual environment which is a copy of the real environment. The image from the virtual environment is superimposed on a monitor displaying the real environment. The camera's zoom and focus rings are incremented through a plurality of values by discrete steps. For each value, the virtual environment's settings are manipulated until the real and virtual images are identical.

Abstract: A method and apparatus for generating a viewport definition for a computer generated image using sensor information relating to a video camera's pan, tilt, zoom, and focus controls. The method generally comprises the steps of: (a) establishing reference points within an enclosed space which is to be used for recording images with the camera; (b) positioning the camera within the enclosed space relative to the reference points such that the camera position can be determined through triangulation with respect to the reference points; (c) developing position data through triangulation which identifies the camera position in a coordinate system relative to the reference points; (d) recording camera orientation data from sensors disposed to detect camera parameters defining the camera's pan, tilt, zoom, and focus settings; and (e) developing a database defining a viewport for the camera defined from a combination of the position data and the camera orientation data. Calculating the viewport (i.e.

Abstract: The present invention is directed to a simulation system for simulating virtual reality experiences such as for the sport of hang gliding or the like. The simulation system has a stereoscopic and collimated virtual image display, for providing pupil forming simulated images to a rider at a fixed point of reference relative to the stereoscopic display. In the disclosed embodiment, the simulation system comprises a mechanical support structure for suspending the rider in a harness so as to allow freedom of movement. The rider is suspended to face a visual display over a movable control bar coupled to the mechanical support structure. By maneuvering the control bar, riders may view the results of their actions as by a simulated display. The visual display is coupled to the control bar to receive electrical signals indicative of the movements initiated by the riders as they maneuver through a programmed environment.

Abstract: A method for rendering a shadow cast from an object illuminated by at least one light source onto at least another object on a graphical computer display. The preferred embodiment enables the rendering of accurate and realistic shadows in real-time, consequently providing a realistic view of three-dimensional objects in two dimensions. The shadow can also provide more visual clues than are otherwise available from ambient light sources. In this way, more visual information is provided to an observer.

Abstract: A system and method improves pixel update performance in computer graphics systems. Pixel sample coverage masks and data record memory locations are assigned to each pixel. The data record memory locations store pixel sample data for one or more pixel samples. A coverage mask is associated with each data record and contains mask bits which identify the pixel samples that are assigned the data contained in the data record memory location. In another embodiment, the pixels are also assigned versions which are compared with a current version. In response to the version comparison, predefined alternate pixel data or pixel data stored in a frame buffer is blended with new pixel data. The blended pixel data is written to the frame buffer from which it is retrieved and displayed by a display device. In another embodiment, pixel data memory is dynamically allocated to reduce the dedicated memory requirements while still providing high quality images.

Abstract: An adaptive pixel multisampler generates pixel data for display using an interlocking sub-pixel sampling pattern and a frame buffer organized as a per-polygon, per-pixel heap. The interlocking sampling pattern provides the advantages of a multi-pixel shaped filter without pixel-to-pixel cross communication and without additional sub-pixels. The per-polygon, per-pixel heap allocates frame buffer memory so that each pixel will have one set of data stored in the frame buffer for every polygon that influences that pixel. This memory allocation scheme can significantly reduce frame buffer memory requirements. The polygon data is blended to properly handle processing of transparent polygons and polygon edges without the degradation of image quality found in conventional computer graphics systems.

Abstract: Improved computer graphics system texture interpolation is provided using texture rules and planar texture interpolation. A texture rule is defined which characterizes texture variation within an area defined by a set of texels. The texture rule is used to select a texture plane which approximates the texture mapped to a pixel. This texture plane is used to generate a texture value for the pixel. In one embodiment, the texture rule identifies a triangle pair defined by four texels. One of these triangles is selected based on the position of the pixel relative to the texels. The pixel is then mapped to the plane defined by the selected triangle and the texture value for the pixel is calculated by interpolating the texture value at the location in the plane to which the pixel was mapped.

Abstract: A dynamic terrain display is created from digitized grid post data as a height field, that is textured using maps embracing progressively larger areas with increasing remoteness from the viewpoint. A truncated pyramid is defined by map parts for each level that are maintained in active memory. The map parts or fragments are stored in rectangular configurations to be updated row-by-row or column-by-column, by overwriting obsolete data in a circular manner to reflect changes in the viewpoint. Levels of the map parts accordingly are paged independently of each other from database storage. Not all levels are required to have texture in that if a level is not available, a lower level can be employed. Theme cells also can be utilized.

Abstract: A computer graphics system is defined using supersampling of multi-level pixel characteristic data. The system provides a detailed anti-aliased display of the texture on surfaces defined at oblique angles within the model space while providing simple real time controls to control the amount of extra processing required for the supersampling. A sampling path is defined within a projected pixel footprint on a textured surface defined in model space. These sample points are mapped to levels of detail and locations within a texture MIP map. The level of detail and supersampling locations are calculated for each pixel that the polygon influences. The sampled texture data is blended forming a single texture value for that pixel. This texture value is blended with other characteristics of the pixel to form the pixel data that is displayed on a display unit.

Abstract: In a multiple-projector concave-screen display system, spacial alignment of images on the screen, is enabled by designating calibration points with retro-reflective dots and illumination markers. The manufacture of the screen involves locating calibration points and depositing the dots with a tool utilizing a rotary mechanism for loading and applying the dots from solenoid actuated pod units. Areas for retro-reflective dots, versus illumination markers, are defined on the basis of reflectance angles between vectors to the screen from a projector and from the screen to a viewer.