Disclosed is a method of rendering a radial gradient blend defined by a gradient function. The method identifies respective first and second radial limits for a point of the radial gradient blend, the respective first and second radial limits having known blend values and receives an estimated value of the gradient function for the point. The method determines a direction from the estimated value to an ideal value, wherein the ideal value is a value of the gradient function for the point and modifies the estimated value, based on the direction of the ideal value. The method checks the ideal value is within a predetermined threshold of the estimated value and stores a determined blend value for the point by interpolating between the known blend values of the respective first and second radial limits on the basis of the modified estimated value of the gradient function, to render the radial gradient blend.