# World Graph Node Editor

A standalone visual node editor for authoring world generation graphs. Built with Dear ImGui and imnodes, styled after Blender's geometry nodes.

## What it does

Graphs describe how tiles are generated for each chunk in the world. Each node is a mathematical or contextual operation — noise functions, arithmetic, comparisons, tile queries — and they connect together into a tree that evaluates to a float value per tile. The game uses this value to decide what tile type to place.

Graphs are saved as Flecs JSON (`graph.json`) and loaded by the game at runtime, where they are compiled into an efficient memory-pooled runtime graph and evaluated per-tile during chunk generation.

## Controls

| Action | How |
|--------|-----|
| Add a node | **Add Node** menu in the menu bar |
| Connect nodes | Drag from an output pin to an input pin |
| Disconnect a link | Right-click the link |
| Pan the canvas | Middle-click drag, or Alt + left-click drag |
| Zoom | Scroll wheel |
| Mark output node | Right-click a node → **Set as Output** |
| Delete a node | Right-click a node → **Delete Node** |
| Save graph | **File → Save** or **Ctrl+S** (writes `graph.json`) |
| Load graph | **File → Load** or **Ctrl+O** (reads `graph.json`) |

The **output node** (highlighted in orange) is the root of evaluation — it must be set before the graph can be compiled by the game.

## Node types

### Math (binary, float → float)
`Add` `Subtract` `Multiply` `Divide` `Modulo` `Pow` `Max` `Min`

### Math (unary, float → float)
`Negate` `Abs` `Ceil` `Floor` `Sin` `Cos` `Tan` `Exp` `Log` `Square` `Round` `OneMinus`

### Math (ternary, float → float)
`Lerp` `Clamp`

### Comparison (float → bool)
`Equal` `Smaller` `Greater` `SmallerEqual` `GreaterEqual`

### Logic (bool → bool)
`And` `Or`

### Control flow
`Branch` — inputs: condition (bool), true value (float), false value (float)

### Noise (no inputs, float output)
`Simplex` `OpenSimplex` `Perlin` `Value` `ValueCubic`

Parameters: **Frequency** — controls the scale of the noise.

### Leaf nodes
| Node | Parameters | Output |
|------|-----------|--------|
| `Constant` | Value (float) | The constant value |
| `IsTile` | RelativeX, RelativeY, TileType | bool — true if the tile at the offset matches the type |
| `TileDistance` | Range (1–3), TileType | float — distance to the nearest tile of that type |

## Graph file format

Graphs are stored as Flecs JSON. Example of a simple graph that outputs Perlin noise:

```json
{
  "entities": [
    {
      "name": "Graph",
      "children": [
        {
          "name": "Perlin_0",
          "components": {
            "VisualNodeType": {"kind": "Perlin"},
            "VisualNodePos": {"x": 100.0, "y": 100.0},
            "NodeParam_Noise": {"frequency": 0.01},
            "VisualNodeOutput": {}
          }
        }
      ]
    }
  ]
}
```

Connections between nodes are stored as Flecs relationships (`InputPin0`, `InputPin1`, `InputPin2`) on the destination node, referencing the source node by name. This makes the JSON human-readable and easy to hand-edit.

## Building

Built automatically as part of the main CMake project:

```sh
cmake -B build
cmake --build build --target node-editor
./build/tools/node-editor/node-editor
```

Dependencies (fetched automatically via FetchContent): GLFW, Dear ImGui, imnodes.