Abstract: According to the 3D-CAD system of the present invention, basic graphic elements (PL, LL, SL, VL) are set based on linear, area or volume coordinate parameters, and the plurality of basic graphic elements are continuously connected to generate a basic graphic. The basic graphic elements constituting the generated basic graphic are continuously differentiable even after deformation, thereby generating a desired solid graphic (identical topology graphic). By using these patches for approximately expressing all surfaces, the surfaces are handled consistently, the data quantity describing the graphics is greatly reduced, and the load of operational processing of the computer is reduced. Whether or not an element can be deleted is determined based on a reference counter RC showing whether said element is the component of another element.

Abstract: A multitrack recording apparatus includes a multi-channel recorder for recording musical timing data on a recording medium, a modulator for variably setting a recording cycle of the musical timing data, and a keyboard for designating a desired search position of the recording medium according to the musical timing data. The apparatus also includes a reproduction head for reproducing the musical timing data from the recording medium, a controller for calculating the driving position of the recording medium on the basis of the reproduced musical timing data and for controlling the driving of the recording medium to stop the recording medium at the designated search position, and a dispaly unit for displaying musical data on the basis of the reproduced musical timing data.