Sprite Scaling on the Master System: Building the New on the Ruins of the Old

8 hours ago

The TMS9918A VDP, used in early Sega consoles, introduced sprite magnification (MAG) for all sprites at once, though it was rarely used.
The Master System's 315-5124 VDP, a descendant of the TMS9918A, inherited sprite scaling but with limitations: only four sprites per scanline can be magnified horizontally, requiring placeholder sprites for proper scaling.
Sprite scaling was omitted in the Sega Genesis's compatibility mode, breaking effects that relied on the 315-5124 VDP's magnification.
The later Master System 2 (315-5246 VDP) fully supported sprite magnification as a coherent feature, with all sprites scaling correctly, and was common in Europe.
Developers are advised to avoid sprite scaling for broad compatibility, considering the varied support across Master System models and the Genesis.
The author implements sprite scaling detection and fallbacks, using placeholder sprites for older VDPs and pre-doubled sprites for the Genesis to ensure playability.

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