Abstract: A method for generating a circular or elliptical arc on a digital computer display (FIG. 1). An ellipse can be generated in two dimensions (FIG. 5) or three dimensions with perspective (FIG. 13). The ellipse dimensions form angle meters (FIG. 4) that provide rotational angle information for a screen point moving along the elliptical curve (FIG. 3). Pixels are colored and antialiased with a texture table (FIG. 2). The drawing loops for two dimensions (FIG. 6) and three dimensions (FIG. 14) are computationally simple and suitable for implementation in a custom designed, dedicated computer circuit. The three dimensional perspective drawing employs a depth constant that fits the curve to the perspective field of view (FIG. 8). As the curve depth changes, the depth constant directs the rescaling of the ellipse (FIG. 11).

Abstract: Apparatus for displaying the frequency spectrum of an audio signal. Multiple filters (20, 24, 25) are employed to divide an audio signal into signals each having a distinct frequency spectrum. The individual signals are combined to provide a composite reference signal. Individual comparators (26, 27, 28) compare each signal with the reference signal and individual light circuits are turned on and off in response thereto. A separation control (32) is provided to alter the magnitude of the reference voltage whereby a variation in separation between lights is achieved.