# Normal mapping

vertex-tangent TBN with a derivative fallback.

```{raw} html
<a class="example-run-button" href="../demos/features_3d_normal_mapping.html">▶ Run in browser</a>

```

**Tags:** `3d`

Two spheres share one procedurally generated normal map (diagonal ridges).
The left sphere has no tangent data, so the renderer reconstructs a tangent
frame from screen-space derivatives. The right sphere calls
``Mesh.generate_tangents()``: its authored per-vertex tangents ride the
extras vertex stream and select the tangent normal-mapping pipeline, the
same path glTF models with TANGENT accessors use. Both paths light the
ridges; the vertex-tangent frame is smooth and view-independent where the
derivative frame is faceted per pixel-quad.

Controls:
    Escape - Quit

Run: uv run python examples/features/3d/normal_mapping.py

## Source

```{literalinclude} ../../examples/features/3d/normal_mapping.py
:language: python
:linenos:
```