Raster Tricks
Exploiting the electron beam
Raster tricks push hardware beyond specifications by precisely timed manipulation during screen display, achieving impossible-seeming effects.
Overview
Raster tricks are raster effects taken further—exploiting undocumented behaviours, cycle-exact timing, and hardware quirks to achieve effects the chip designers never intended. The demoscene pushed these techniques furthest, displaying more colours, more sprites, and more complex effects than any specification promised.
Fast facts
- Beyond spec: effects exceeding documented capabilities.
- Timing: cycle-perfect precision required.
- Discovery: often through experimentation.
- Demoscene: primary developers of techniques.
- Documentation: initially secret, now shared.
Advanced techniques
Beyond basic raster effects:
- FLI (C64): flexible line interpretation for more colours.
- VSP (C64): vertical position manipulation.
- Border sprites: sprites in normally impossible areas.
- Copper tricks (Amiga): complex display manipulations.
Why they work
Exploiting hardware:
- Undocumented registers: behaviours not in manual.
- Timing windows: brief moments to change state.
- Race conditions: beat the hardware to changes.
- Side effects: using bugs as features.