Abstract: A method and apparatus for simulating the effect of non-homogeneous fog in an image displayed on a screen. The image is intended to represent the appearance of a model defined in a database in world space coordinates from an eyepoint position in world space, the model being defined in terms of individual features each having predetermined attributes defining the position and visible characteristics of the feature. Image data is derived from the model for each of an array of sampling points distributed across screen space. A non-homogeneous fog structure is defined in world space coordinates as a series of parallel strata of predetermined extinction coefficients. The positions of the eyepoint and a feature to be displayed relative to the fog structure are determined. The distance from the feature to the eyepoint is calculated.

Abstract: An actuator assembly comprising a pair of interconnected extensible actuators defining two sides of a triangle structure, and a linkage constrained to move with the actuators such that differences in extension of the actuators cause a change in position of the linkage. Changes in position of the linkage are detected to enable relative actuator extensions to be monitored.

Abstract: A method and apparatus for simulating the effect of non-homogeneous fog in an image displayed on a screen. The image is intended to represent the appearance of a model defined in a database in world space coordinates from an eyepoint position in world space, the model being defined in terms of individual features each having predetermined attributes defining the position and visible characteristics of the feature. Image data is derived from the model for each of an array of sampling points distributed across screen space. A non-homogeneous fog structure is defined in world space coordinates as a series of parallel strata of predetermined extinction coefficients. The positions of the eyepoint and a feature to be displayed relative to the fog structure are determined. The distance from the feature to the eyepoint is calculated.

Abstract: A method and apparatus for simulating the illumination effects of a vehicle-mounted light source in an image displayed on a screen. The image is intended to represent the appearance of a model defined in a database in world space coordinates from and eyepoint position in world space, the model being defined in terms of a plurality of features each having predetermined attributes. The vehicle-mounted light source is defined in terms of an origin and a direction in eyepoint space. For each feature potentially contributing to the image, the angular position of a point on that feature relative to the light source is calculated as the angle between the light source direction and a line drawn to that point from the light source. An illumination intensity for that point is determined by reference to the calculated angle, and the illumination intensity is reduced as a function of the distance from the eyepoint to the said point to provide a resultant intensity.

Abstract: An apparatus for generating an image from data defining a model including a plurality of opaque and translucent features. The image is intended to represent a view of the model from a predetermined eyepoint and is made up from an array of screen space pixels. The image area is divided into an array of sub-areas each of which covers at least one pixel. For each feature in the model that is potentially visible from the eyepoint, a test is conducted to determine which of the sub-areas is at least partially covered by that feature. For each feature which covers a sampling point, a function of the distance from the eyepoint to that feature at the sampling point is determined. An output for each pixel within a sub-area is produced, the pixel output corresponding to the combined effects of the sampling point outputs for all sampling points which contribute to that pixel, and the pixel outputs are displayed.

Abstract: Elliptical features are described in an image generator database in terms of an origin and major and minor axes defined by reference to a world or model space coordinate system. Image data is assembled for display by transforming the database contents into screen space and assessing for each of an array of sampling points distributed across screen space which features are to contribute to the portion of a final image in which the sampling point is located. In the case of elliptical features, data is transformed into eyepoint space and each sampling point is projected into eyepoint space to determine the point of intersection between a line drawn through the sampling point from the eyepoint and a plane defined by the axes. The coordinates of the intersection point in a coordinate system defined by the origin and axes, are used to determine whether or not the feature contributes to the sampling point.

Abstract: A method for assembling a simulator in which a visual display system is arranged to display an image for viewing from a predetermined viewing position within a simulated viewing station. The visual display system and viewing station are mounted on a base. The viewing station is fabricated such that the location of the viewing position relative to the viewing station is established. The visual display system is fabricated so that when mounted in a predetermined position on the base the location of the viewing position relative to the base is established. When the viewing station and visual display system are mounted on the base, the visual display system is mounted in the predetermined position, and the viewing station being mounted at a position relative to the base selected such that the eye position of a person sat within the viewing station coincides with the location of the viewing position relative to the base.

Abstract: A field blanking pulse modifier in which the line synchronizing pulses and the field blanking pulse of a conventional television signal are derived. A counter is arranged to be reset by the field blanking pulse and to count the detected line synchronizing pulses or multiples thereof. An offset count is set corresponding to half the desired difference in duration between the modified field blanking pulse to be generated and the field blanking pulse of the television signal. The generation of the modified field blanking pulse is initiated when the sum of the counter content and the offset count is equal to the counter content which results after the counting of all the line synchronizing pulses between two successive field blanking pulses of the television signal, and the generation of the modified field blanking pulse is terminated when the counter content is equal to the offset count.

Abstract: A simulator for simulating radar or sonar signals returned to an observation point from a three-dimensional object of non-uniform reflectivity. An imaginary three-dimensional object is defined spatially in the form of a series of three-dimensional regularly shaped elements. Each element has allocated to it a predetermined level of uniform reflectivity.The position of boundaries of the element along an imaginary radial line extending from the observation point are calculated and the reflectivity allocated to points on the line on each side of each of the boundary positions is calculated. A sequence of signals is then generated which is representative of the allocated reflectivities occurring along the length of the line.

Abstract: A system and method for limiting the motion of the motion platform of a vehicle simulator in which the motion platform is supported on a plurality of extensible members, the extension of the members being controlled by commands initiated by a user of the simulator. At least one absolute limit is set for at least one parameter such as position or velocity of the extension of each of the members, and the parameter is maintained within the limit. The commanded or actual magnitude of the parameter is monitored for each member relative to that members absolute limit, the member for which the monitored relative magnitude is the greatest is determined, and the limit determined for each of the other members is scaled down such that a movement of the motion platform which causes the parameter for any one member to reach its absolute limit also causes each of the other members to reach its scaled down limit at the same time.

Abstract: An acousto-optic scanner comprising at least two optical sources the outputs of which differ in frequency, a common acousto-optic deflector, a scan lens, and scan correction means. The output of the light sources are directed through the common acousto-optic deflector and the outputs of the common acoustic-optic deflector are directed through the scan correction means which comprises a plurality of optical elements. The effect of the optical elements on optical beams is dependent upon beam characteristics.