Patent GB-1437795-A (GB)
Title: Digitally controlled computer animation generating system
IPC: G06T13/40
Filed: 1973-07-04
Abstract: 1437795 Cathode-ray tube displays; television COMPUTER IMAGE CORP 4 July 1973 31924/73 Headings H4F and H4T In an arrangement for producing an animated sequence of an image, the sequence occupying a plurality of frames, signals representing data specifying image parameters for the first frame and for the last frame of the sequence are generated and fed to a computer which is programmed to calculate the parameter data for the intervening frames required to produce a desired animation sequence. Colour may be assigned to the image and it may be displayed against a colour background. The image may be produced by intensity modulation of the beam of a cathode-ray display tube as it scans a plurality of raster sections, one section for each movable element of the image, or the (displayed) raster sections themselves may form the image. When the image is produced by intensity modulation of the raster sections, "art-work" 618 (Fig. 8) is scanned by a television camera to produce corresponding video signals for intensity modulation of the beam to produce the image such as the figure shown in Fig. 9. To produce this figure (the first of a sequence), an operator employing analogue controls such as potentiometers causes analogue and digital signals defining the parameters of the raster sections 610-615 (Fig. 11) to be generated and stored in the computer. The parameters of the raster sections (Fig. 12) corresponding to the last figure in the sequence (Fig. 10) are then generated in similar manner and also stored in the computer. The latter, in accordance with a predetermined programme, then computes the parameters of successive raster sections corresponding to intermediate positions of the figure and these parameters are also stored in the computer. The number of intermediate positions is determined by the speed at which the figure is intended to "walk". Assuming that the figure should change from the attitude of Fig. 9 to the attitude of Fig. 10 in one second a total of thirty intermediate positions is required when the display is to be produced by a 30 frameper-second television system whereas, if the sequence is to be filmed, 24 frames are required. In displaying the sequence analogue outputs from the control system (controlled by the computer) operate on the X and Y deflection circuits of the display tube to cause the display of the complete sequence of frames the various raster sections of which are intensity modulated (by discrete grey levels) by video signals derived by scanning the "art-work" 618, the order of scanning being controlled by the computer in accordance with the order in which the different raster sections are scanned. Analogue outputs also control an overlap network to prevent the display of "overlapped" positions of the image. Additionally the computer may supply signals specifying the colour components of colours to be assigned to each discrete grey shade of the image. If desired background information in T.V. format and which may be in (NTSC) colour may be combined with the sequence of image signals. The display may be recorded locally on video tape and also be transmitted by microwave link to a remote video tape recorder. The red, green and blue components may also be recorded on respective black/white film. The control system, in addition to controlling the orientation, position, length and spacing of the lines of each raster section, produces "bending" of the raster lines by means of a vertical "modulation" and produces horizontal distortion effects by means of horizontal "modulation" to vary the rate at which raster lines are scanned. Additionally, a "depth modulation" is employed to create depth distortions equivalent to the foreshortening effects produced by wide angle lenses and beam intensity compensation is provided to compensate for variations due to changes in size of the image and of the scan velocity and variations occurring in the operation of the overlap network. The complete operation is described with reference to Figs. 1 to 7 (not shown).