# GoRayTracer

CPU ray tracer in Go — a port of Peter Shirley's *Ray Tracing in One Weekend*. Renders spheres with material scattering and outputs a PNG.

## What it does

- **Geometry:** `Vec3D`/`Ray`, `Sphere` + `HitableList` (closest-hit search) — `hitable.go:19`, `camera.go:12`
- **Camera:** pinhole with vertical FOV (90° by default) and aspect ratio — `camera.go:12`
- **Materials:** `Lambertian` (diffuse), `Metal` (fuzzed reflection), `Dielectric` (glass, Schlick approximation) — `material.go:13`
- **Rendering:** recursive `RayColor` with `MaxDepth=50`, `RaysPerPixel=10` stochastic anti-aliasing, gamma correction (`sqrt`) — `color.go:34`
- **Output:** `Frame [1000][2000]Pixel` sky gradient background, saved as PNG via `image/png` — `image.go:19`

Default scene (`main.go:35`): two `Lambertian` spheres (blue/red, radius `cos(π/4)`). Two alternative scenes are commented in `main.go:40` (metal/glass + ground sphere, and an animation loop).

Constants in `main.go:11`: `Width=2000`, `Height=1000`, `TMin=0.001`, `TMax=1000`, `RaysPerPixel=10`, `MaxDepth=50`.

## How to run

Prerequisite: [mise](https://mise.jdx.dev/) (installs Go automatically) or Go 1.27+.

```sh
# with mise (recommended)
mise install          # installs Go 1.27
mise run run          # go run . → writes img.png (~5s, 2000×1000)
mise run build        # builds ./goraytracer
./goraytracer         # same as above

# with Go directly
go mod tidy
go run .              # → img.png
go build -o goraytracer . && ./goraytracer
```

Output is `img.png` (2000×1000 PNG, excluded by `.gitignore`). Check/lint:

```sh
mise run check        # go fmt + go fix -diff + go vet + go build
```

## Customizing

Edit `main.go` to swap the `World` definition (uncomment the 4-sphere or animation blocks), or adjust `Width`/`Height`/`RaysPerPixel` for faster previews (e.g. 400×200).