How to use
- Copy the installation command and review the source package before installing it in your own agent environment.
- Check the source document for required tools, credentials and supported hosts.
- Describe your input and desired deliverable; review the output against the source material.
npx skills add https://github.com/ewrogers/megadev-skills --skill megadev-rasterBefore you start
- Installation does not include a model subscription, API allowance or permission to access your files.
- Repository stars and installation counts describe activity, not an independent quality or security test.
Rendered from the source repository. Headings, examples, code, tables, links, and referenced images are preserved.
Megadev raster effects
Use raster effects when the design needs different display state within a frame. Mega CD still uses the Mega Drive VDP: extra CPUs, Word RAM and the ASIC do not add palettes, planes, sprite capacity or a second independent display. The Labs' scenery, audio, controls and split sizes are illustrative.
- Read Interrupt ownership and timing before installing
a handler or changing VDP state during display.
- Read Water and split-screen for reflected tilemaps,
line scroll, palette pairs, camera transforms and seam/sprite budgets.
- Read Validation for failure tests, regional builds,
emulator checks and physical-hardware limits.
Inspect actual source in ewrogers/megadev:latest. The Lab's rt_* functions and raster_* assembly are application code, not Megadev raster APIs. Do not import SGDK interrupt, DMA-queue or sprite-engine calls.
Essential rules:
- Reuse the game's VBlank, input, audio and Main/Sub service owners. One owner
schedules VDP access; an H handler must not compete with foreground uploads.
- Build an immutable frame outside interrupts. Commit its line, scroll, palette
and seam sprites together, then latch a dedicated HBlank plan in VBlank.
- Restore dry/top state early in VBlank. Program the next counter before bulk
uploads, finish within a measured blank interval, then arm the current epoch. Reject pending blank-edge/early interrupts without consuming that plan.
- Keep HBlank assembly short and bounded. Save used registers, return with RTE,
and perform no BIOS, C, allocator, CD or decoder calls there. Bound edge polling and interrupt masking; reject late writes rather than coloring another frame.
- Minimize active-display CRAM writes. Prefer prepared palette banks and line
scroll; if needed, preload a tiny color pair and write on a fresh HBlank. A foam sprite can hide the seam, but cannot excuse an unbounded palette upload.
- Split-screen shares planes, SAT, palettes and VRAM. Transform and clip sprites
for each view, budget scanlines, and explicitly reserve divider rows.
- Measure repeated movement and boundary cases, not just a fixed waterline.
Emulator success does not prove CRAM-dot absence or interrupt/bus timing on physical hardware. Offer an effect-off comparison and a simpler fallback.
Raster Labs generate separate water and split discs with scripts/create_project.py --demo water|split. The renderer uploads resident art once and bounds steady-state DMA. Reuse megadev-graphics for general VDP rendering, megadev-system for Main/Sub work, megadev-audio for audio ownership and megadev-performance/megadev-hardware for broader qualification. This skill owns scanline scheduling and the within-frame transforms, not those systems.
