---
skill-group: geometry
skill-order: 1
---

# Coordinate System Convention

ForgeCAD uses a **Z-up** right-handed coordinate system.

For objects with a clear facing direction, model the front/face/nose/camera side toward **-Y**. The rear/back side is **+Y**. In code, a forward/fore direction vector is `[0, -1, 0]`.

## Axes

| Axis | Direction       | Positive |
|------|-----------------|----------|
| X    | Left / Right    | Right    |
| Y    | Front / Back    | Back     |
| Z    | Up / Down       | Up       |

## Standard Views

The camera position direction says where the camera sits relative to the model. A front view camera sits at `-Y` and looks toward `+Y`, so it sees the model's `-Y` front face.

| View   | Camera position direction | Sees plane |
|--------|---------------------------|------------|
| Front  | -Y                        | XZ         |
| Back   | +Y                        | XZ         |
| Right  | +X                       | YZ         |
| Left   | -X                       | YZ         |
| Top    | +Z                       | XY         |
| Bottom | -Z                       | XY         |

## GizmoViewcube Face Mapping

Renderer/view-cube internals may have their own material ordering. Map any view-cube labels to the ForgeCAD directions below:

| Direction | ForgeCAD label |
|-----------|----------------|
| +X        | Right          |
| -X        | Left           |
| +Y        | Back           |
| -Y        | Front          |
| +Z        | Top            |
| -Z        | Bottom         |

The face/anchor API is the source of truth: `front` resolves to the minimum-Y side and `back` resolves to the maximum-Y side.

## Grid

The ground plane is XY (Z = 0). Extrusion goes along +Z. Manifold is Y-up internally — if a kernel-facing operation behaves as if axes are swapped, check for Manifold Y-up semantics leaking through.
