Posted By
TCFS
on 2023-10-01
15:05:54
 |  Re: Tamás Sasvári comes back with a port of last years C64 Remake from "The Empire Strikes Back"
Hi seff,
Short summary:
- All stuff use charset (only the main title screen with the AT-ATs and the studio logo are bitmaps)
- The game uses standard multicolor mode (hud and radar are hires with some raster trick to increase color density)
- My sprite engine uses double frame buffering
- Different scroll speeds are implemented mainly with raster interrupts, where the player is not crossing the raster cuts; top clouds and the fastest bottom foreground terrain is a pure raster-ineterrupted scroll.
The only place where you can cross terrain elements different speeds is the one between the distant hills and the main ground, where the ATs are walking on. The "distant hills zone" is a special purpose sprite (40 characters wide) to be able to move horizontally in pixels with different speed. The ATs are not sprites, they are using the advantage of the distant hills being a sprite, the hills are masking behind the ATs, giving the illusion that the ATs are the sprites masking on the hills. Sometimes - in order to reduce color clash - the distant hills zone turns off bitwise masking of ATs on some character positions. Frame-by-frame the sprite engine decides which positions are in danger of color clash and controls the masking behavior dynamically to ensure the best visual experience.
- The sprites (player, probe droids, bullet, rocket, explosion) are not precomputed, they are shifted on the fly. I don't use negative masks, my sprite engine is able to combine masked bytes properly, taking the multicolor pixel pairs into consideration.
- Refresh rate is dynamic, somewhere between 25 and 12, based on the screen occupancy.
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