What? Behind the image that is being drawn on your screen is the function color = y³sin(2*PI*x*e^5*x). Sampling is a method of assigning color values to the image area based on the function. The computer can only calculate the color for a few points in the image, then assign that color to the area around the point. Regular sampling picks a point in the middle of a box to compute the value of the color. Box filtering means every point inside that box is now assigned the color calculated for the point in the middle. The next applet in this series shows different types of sampling and filtering.