# Post shader

full-screen user GLSL over a pure-2D scene.

```{raw} html
<a class="example-run-button" href="../demos/features_2d_post_shader.html">▶ Run in browser</a>


```

**Tags:** `2d` `post-process` `shader` `glsl` `environment`

A ``WorldEnvironment`` plus a ``PostProcessEffect`` runs a body-only GLSL
fragment over the finished 2D frame: three orbiting polygons over a line grid,
warped by an animated ripple with a scanline flicker. The shader ABI is
automatic: ``u_time``, ``u_resolution``, ``u_colour_tex`` (and ``u_depth_tex``)
arrive as uniforms, output goes to ``frag_colour``, and any extra uniform is
live via ``set_uniform`` each frame (the ripple strength breathes this way).
Screen-space HUD text (``Text2D``) composites after the effect, so it stays
crisp while the world warps.


## What it demonstrates
- ``PostProcessEffect`` with body-only GLSL on a scene with no 3D content.
- The automatic uniforms and the ``frag_colour`` output convention.
- Animating a user uniform per frame with ``set_uniform``.
- Toggling the pass live via ``effect.enabled``.

Controls:
  E   - Toggle the post-process effect
  ESC - Quit

Run: uv run python examples/features/2d/post_shader.py
Headless self-check: uv run python examples/features/2d/post_shader.py --test

## Source

```{literalinclude} ../../examples/features/2d/post_shader.py
:language: python
:linenos:
```