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Co-authored-by: bQUARKz <bquarkz@gmail.com>
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2026-04-10 05:31:57 +00:00

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GFX Mental Model

Status: pedagogical Companion spec: ../specs/04-gfx-peripheral.md

Related asset spec: ../specs/15-asset-management.md

PROMETEU treats graphics as an explicit peripheral, not as a modern GPU.

The right mental model is a retro 2D machine with:

framebuffer;
glyph banks;
tile layers;
sprites ordered by draw order;
deterministic composition per frame.

Why This Exists

The goal is not to imitate historical hardware byte for byte. The goal is to capture the family of constraints and visual language of consoles such as SNES, CPS-2, and Neo Geo in a small, portable contract that can run on desktop and DIY hardware.

That produces some important consequences:

draw order matters more than "effects";
palettes matter as part of asset design;
the programmer thinks in terms of rasterization, not shaders;
visual cost becomes more observable.

What The GFX Is Not

PROMETEU GFX is not:

a modern GPU pipeline;
an RGBA framebuffer with arbitrary alpha;
a shader system;
automatic post-processed composition.

Those absences are deliberate. They force a visual language closer to classic consoles and keep the contract executable in modest environments.

Practical Intuition

Tile layers exist for world and scenery.
HUD exists for fixed information and should remain decoupled from the camera.
Sprites exist for moving entities, and their depth depends on order and priority.
Palettes exist to vary visual state without duplicating tile art.
Fade exists as a discrete special effect, not as generic alpha.

Palette Thinking

A good way to think about PROMETEU is that art and color are not the same thing.

The tile is the shape. The palette is the visual state.

That enables:

enemy variation;
biome changes;
damage, ice, poison, power-up states;
HUD themes;
day and night cycles.

In the current glyph-bank v1 baseline, this palette model is intentionally bounded:

each bank carries 64 palettes;
each palette carries 16 colors;
palette_id is therefore a small runtime-facing selector, not an open-ended color namespace.

That limit is not incidental bookkeeping. It is part of how art packaging, runtime validation, and rendering stay aligned.

Glyph Banks Are Decoded Runtime Objects

The most useful intuition is to separate three layers:

authored indexed art;
serialized cart payload;
resident runtime bank.

For glyph banks in v1:

authored pixels are logical indices 0..15;
serialized payload stores those indices as packed 4bpp;
runtime memory expands them to one u8 index per pixel after decode.

So when reading the graphics model, do not imagine the renderer reading packed nibbles directly from cartridge storage. The renderer consumes a decoded GlyphBank object whose memory shape is optimized for runtime lookup, not for transport density.

Use Cases

area transition with Scene Fade;
HUD transition with HUD Fade;
damage flash or teleport flash;
global palette swap for weather or world state.

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