## 2. What option 10 shows

The bot is a 192-triangle sphere with its eyes painted onto a texture. It sits among three wooden crates on a stone floor. The camera orbits.

Each checkbox switches one PS1 flaw on or off. Tap "Modern fix" to correct them all at once, then "PS1 look" to restore them.

| Flaw | What you'll see | Why the PS1 did it |
|---|---|---|
| Affine texture warp | Floor tiles zig-zag and bend along a diagonal | No per-pixel divide; textures were stretched in screen space |
| Vertex snapping | Edges shimmer and crawl as the camera moves | Screen positions were whole pixels only |
| 15-bit dither | Fine checker grain in the fog and shading | 32,768 colours, with a fixed 4×4 dither pattern hiding the banding |
| No depth buffer | Crates can pop in front of the bot at wrong moments | Triangles were sorted by average depth instead |
| Fog | Distance fades to blue-grey | Hid the short draw distance |
| Gouraud shading | Smooth light across faces (untick for faceted) | Lighting per corner, blended across the face |

## 3. Try these experiments

1. **Untick "Subdivided floor"** (the PS1 default here). The whole floor is just 2 triangles, so the warp is extreme. Tick it: 128 smaller triangles hide most of the warping. Real PS1 developers split floors like this for exactly that reason.
2. **Drag camera distance to 3.2.** Warp and wobble grow as you get closer.
3. **Watch the eyes.** They're on the texture, so affine warp bends them slightly as the bot turns.
4. **Untick only "Vertex snapping."** The shimmer stops but the texture warp stays. The two flaws have separate causes.

## 4. Less obvious details

- **The blob shadow is period-accurate.** PS1 games rarely had real shadows. A dark disc under the character gave depth for almost no cost.
- **Blinking swaps textures.** The model never changes. The engine swaps between two 128×64 textures, one with open eyes and one with slits. Many PS1 characters had rigid faces for the same reason.
- **The dither pattern is the real one.** The same 4×4 offset matrix the hardware used, applied before rounding each channel to 5 bits.
- **Clipping is the one thing I fixed.** Triangles crossing the camera's near plane get cut properly here. On the PS1 they often vanished or tore when you got too close to a wall.

## Examples

**Affine vs perspective-correct**
```
affine (PS1):      u = w0·u0 + w1·u1 + w2·u2            ← linear on screen
perspective:       u = Σ(w·u/z) ÷ Σ(w/z)                ← divide per pixel
                   one extra divide per pixel = too slow in 1994
```

**Frame pipeline**
```
mesh → scale/rotate → light per vertex → view space
     → clip near plane → project (round to pixel if snap)
     → sort by depth (or depth buffer) → rasterize
     → texture (affine?) × light → fog → 4×4 dither → 5-bit per channel
```

**Floor subdivision**
```
1 quad = 2 tris          8×8 grid = 128 tris
┌───────────┐            ┌─┬─┬─┬─┐
│        ╱  │  warp is   ├─┼─┼─┼─┤  each piece warps
│    ╱      │  one big   ├─┼─┼─┼─┤  a little → errors
│ ╱         │  bend      └─┴─┴─┴─┘  stay tiny
└───────────┘
```