GLSL code blocks for Emacs Org-mode

This org-mode extension adds the capability to run GLSL code blocks directly from inside Emacs and immediately displays the rendering results inline in your org-mode buffers.

Requirements

• SDL2 (for creating OpenGL context)
• SDL2_image (for saving PNG files)
• glbinding (for OpenGL SDK)

The rendering is done with OpenGL 3.3 so should work on any graphcs card.

Building

1. Generate project with CMake:

   cmake -G "Ninja" .
       

2. Build the code:

   ninja
       

This will create the Emacs dynamic module ob-glsl-module.so (Linux) or ob-glsl-module.dll (Windows) or ob-glsl-module.dylib (MacOS).

Installing

1. Put both ob-glsl.el and the dynamic module under your elisp load path.
2. Add (glsl . t) to org-babel-load-languages. You can either customize the variable or add it manually in lisp code.

Supported parameters

• :file The output file path (required)
• :width The render width in pixels
• :height The render height in pixels

You can omit either :width or :height and the omitted one will be calculated based on the other parameter. If you omit both, then the default output size is 400x300.

A simple pixel shader example

vec3 mandel(vec2 z0) {
    float k = 0.0;
    vec2 z = vec2(0.0);
    for(int i = 0; i < 420; ++i) {
        z = vec2(z.x*z.x-z.y*z.y, z.x*z.y*2.0) + z0;
        if (length(z) > 20.0) break;
        k += 1.0;
    }
    float mu = k + 1.0 - log2(log(length(z)));
    return sin(mu*0.1 + vec3(0.0,0.5,1.0));
}
void main() {
    float ar = iResolution.x / iResolution.y;
    vec2 uv = gl_FragCoord.xy / iResolution.yy - vec2(0.66 * ar, 0.5);
    // uv = uv * 2.0 + vec2(-0.3, 0.0);
    float p = 30.0;
    float t = mod(13.0, p);
    if (t > p/2.0) t = p - t;
    float scale = 0.5 + pow(2.0, t);
    vec2 offset = vec2(-1.36799, .01);
    uv += offset*scale;
    uv /= scale;
    fragColor = vec4(mandel(uv), 1.0);
}