Scrolling viewport

I need to scroll the objects as the stunt rider jumps the buses in order to allow a reasonable number of buses to be jumped. the original Atari arcade machine had 28 buses. I did some test of what this would look like and now I’ve started building the first iteration of the framework that will enable a scrolling viewport.

The system is relatively simple and requires using a double word (16 bits) to represent the location of all sprites and objects. this gives a playfield of 65536 positions. An associated viewport position is also represented using the same 16 bit format. It’s actually quite trivial to check to see if an object is withing the current viewport region as the width of the viewport spans a byte (0-255 points).

It’s quite an interesting effect and allows a lot of possibilities. There is a cost associated with this work but it allows quite complex scenes to be developed with minimal hackery.

I now need to finished the manager that has been partly built to enable this little demo, this will then enable me to finish work on the logic and jumping mechanics.

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