# Dynamic procedural sky

a Preetham analytic day-night sweep driving IBL.

```{raw} html
<a class="example-run-button" href="../demos/features_3d_dynamic_sky.html">▶ Run in browser</a>

```

**Tags:** `3d` `sky` `procedural` `preetham` `ibl` `lighting`

Setting ``WorldEnvironment.sky_mode = "procedural"`` (design D12) makes the
renderer synthesize a Preetham analytic sky cubemap from the scene's first
DirectionalLight3D (the sun), its ``sky_turbidity`` (atmospheric haze) and its
``sky_ground_albedo`` (ground bounce). The cube drives BOTH the skybox
background (horizon gradient + a warm sun disc, fading to night as the sun sets)
AND the image-based lighting: the metal and rough spheres pick up the sky's
colour and the sun's glint through the split-sum IBL path, re-baked incrementally
as the sun sweeps. No cubemap texture asset is loaded: the whole sky is closed
form. Press SPACE to pause the sweep.


Usage:
    uv run python examples/features/3d/dynamic_sky.py

## Source

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