PICTURE ELEMENT STRING EXPANDING SYSTEM FOR PARAMETRIC CUBIC CURVE

PURPOSE:To describe a curve having no breaks by determining a difference step width for successive application of a recurrence formula of the forward difference method based on maximum value information of the differentiated function of a parametric cubic curve. CONSTITUTION:An optimum difference step width setting means 1 sets a difference step width most suitable for repeated operation of the recurrence formula of the forward difference method from inputted coefficients and gives the set difference step width to a recurrence formula initial value calculating means 2. This means 2 calculates the initial value of the recurrence formula of the forward difference method in accordance with the coefficients given from a parametric cubic curve generation source and the set optimum difference step width. This initial value is given to a recurrence formula executing means 3, and parameters are changed at intervals of the optimum difference step width to repeatedly execute the recurrence formula in the forward difference method. Thus, vicinity continuity between picture elements is secured with respect to an expanding picture element string, and the output free from breaks is executed.