ShaderDump

ShaderDump is a lightweight command-line tool (in Python) for rendering ShaderToy GLSL fragment shaders to image sequences, suitable for conversion to video. It is GPU accelerated and supports supersampling, as well as any target resolution/framerate. Images can be output in any format supported by the Pillow image library (PNG, JPG, etc.)

I wrote this script because all the other ones I could find on the web were broken. This one will be broken too someday, but for the moment it works.

Note: The current version of ShaderDump does not produce correct output for shaders that depend on ShaderToy.com assets (textures, etc.).

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Input

Just paste your entire ShaderToy fragment shader code into a .frag file. For example:

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;
    float c = 0.5 + 0.5*cos(iTime + uv.xyx + vec3(0,2,4));
    fragColor = vec4(c,1.0);
}

Note: Do not include a #version line or main() function — ShaderDump wraps your code automatically.

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Dependencies

Python 3.7+ is required. Install dependencies via:

pip install moderngl numpy pillow

You may also need to install an OpenGL driver or use a software renderer (e.g., Mesa) if you're running on a headless system (but should be able to run from the command line if you have a display).

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Usage

./shaderdump.py -i myshader.frag

Optional arguments

Flag	Description	Default
-i, --input	Path to input .frag file containing your ShaderToy code	required
-o, --output	Output path pattern using printf-style formatting	./out%04d.png
--fps	Frames per second	60
-t0, --startTime	Start time in seconds	0.0
-t1, --endTime	End time in seconds	1.0
-w, --width	Output image width	1920
-H, --height	Output image height	1080
--supersample	Supersampling factor (antialiasing)	2

Example with full control:

./shaderdump.py \
  -i mandelbrot.frag \
  -o frames/zoom_%04d.jpg \
  --fps 60 -t0 0 -t1 10 \
  -w 1280 -H 720 \
  --supersample 2

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Convert to Video

Once rendered, you can convert frames to a video using ffmpeg:

ffmpeg -framerate 60 -i frames/zoom_%04d.jpg -c:v libx264 -pix_fmt yuv420p zoom.mp4

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Disclaimer

This script was largely authored with the assistance of an AI language model (ChatGPT 4o). It has been tested only lightly, and may contain bugs or edge cases that are not fully handled. Please report issues or submit pull requests to improve robustness.

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License

MIT License. See LICENSE file.