Ep. 07 - Commodore 64 IRQ Lesson 2 : Raster bars and Smooth Scrolling
In this video I'll show you how to create smooth raster bars and a smooth scroller using C64 Studio.
NOTE: There is an error in the video. The proper method is to scroll 8 pixels not 7 and then do a physical move of the letters from right to left.
The concept is, we chain the interrupts together as needed, exiting them using $EA81 to avoid unnecessary delays. The final IRQ call exits at $EA31 as no precision timing is needed then. Chaining involves pointing the vector at $314/$315 to the next interrupt. Location $D016 (53270) is set to 200 (default) at the top of the screen and then uses PIX as a variable to store into $D016 when at the smooth scroll raster line. PIX is decremented causing that area of the screen to shift left and then move the letters left, after 8 pixel shifts.
Full source code:
https://webdrive.commodoregames.net/S...
C64 Studio:
https://github.com/GeorgRottensteiner...