williams-et-al-1983-apple-ii-computer-graphics

13Advanced MovesObjectivesAfter reading Chapter 13 you should be able to:• Use pre-calculated tables to help enhance your animation.• Animate stationary figures using partial modification.• Develop pre-shifts fo r shapes and use them for animation.We commend you for getting this far in your study of Apple II graphics.(No fair if you just skimmed to this point!) You have progressed from aknowledge of BASIC through the land of binary and hex numbers, onthrough the memory map maze, and to the realm of Low-Res graphics.From there you progressed to the world of Hi-Res where you investigatedcolor, shapes, shape-table animation, and byte-move animation.You have seen most of the major schemes currently used to produce Hi­Res graphics, and we think you are ready for a few advanced techniq ues.In this chapter we will look at three different methods which can increasethe speed and efficiency of your graphics. Though the ideas discussed maybe applied in either BASIC or machine-code, the examples are presentedin BASIC for simplicity. The amount of benefit derived from each techniquewill depend on the particular application, and may vary from a lot tonone at all (or worse). However, since a great amount of time spentprogramming any game is devoted to cleaning up the graphics, sometimesyou have to be satisfied with several small improvements.We will start with the idea of partial modification, where instead ofredrawing the entire figure each time, you only plot those bytes whichhave changed from the previous figure. A good illustration of this idea is147