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.

Abstract: Front end processors in a graphics architecture execute parallel scan conversion and shading to process individually assigned primitive objects for providing update pixels. A crossbar along with groups of first-in-first-out registers (FIFOs) accommodates data flow to parallel pixel processors with associated memory capabilities (frame buffer banks) where visibility and blending operations are performed on predetermined sequences of update pixels to provide frame buffer pixels and ultimately display pixels. The pixel processors identify with sequences of pixels in the display in patterns designed to equalize processor loads for pixels located along scan lines of a raster, or distributed over an area. Update pixel data is tagged to identify FIFO groups (pixel processors) individual FIFO selection and output sequence. Temporal priority is accomplished so that primitive data is entered in the frame buffer banks (components) restored to the same order as generated at the central processor (CPU) level.

Abstract: Objects contending for representation in pixels of a graphics display selectively are awarded a fractional area within a pixel on the basis of: coarse calculations in the Z dimension, aggregate demands of the objects and blending techniques free of binary position resolutions. Specifically, the area occupied by a polygon within a pixel is represented using a single number .alpha., which may variously be defined, for example, a value of "0" indicates no area occupied within the pixel, while a value of "255" indicates full pixel coverage. Fine calculations in the Z dimension for binary resolutions are avoided by the blending techniques with attendant antialiasing. A chain of mixer units for storage and blending in pipeline processing compensate the non-associative characteristic of repeated blending.

Abstract: In an area of interest (AOI) display, a detailed image is projected on a screen at the area of interest while a background image is projected on the surrounding area such that the boarder between the two areas varies in an orbital oscillating pattern to accomplish visual blending. A combiner includes a transparent portion to accommodate projection of the background image at the area of interest. The opaque portion carries a mirror to reflect the detailed image filling the area of interest. The combiner is oscillated in an orbital pattern at a resonant frequency, e.g. 210 Hertz by a three phase electromechanical drive unit.

Abstract: A computer-aided design system and a process generates a graphic display of a blend between a plurality of geometric primitive shapes including other blends. An interactive terminal controls a geometric modeler to generate and modify visual graphic displays of primitive geometric shapes at a display screen of the interactive terminal. Logic structures generate both a blend and blends. Each logic structure is implemented with an individual distinct blending algorithm to accomplish a localized superelliptical blend and blends according to user selections including: a plurality of geometric primitive shapes to be blended, a blend operation, and a blend function. A memory, registers and gates in the system store and manage data.