Document grid_lines function

hello-world/assets/shaders/procedural_grid.wgsl

@@ -12,6 +12,18 @@ fn inv_lerp(a: f32, b: f32, v: f32) -> f32 {
     return (v - a) / (b - a);
 }
 
+/// Draw grid-lines at a given scale and camera depth.
+///
+/// @param pos  The reference coordinates for the grid lines.
+/// @param depth  Distance of the camera from the fragment being shaded.
+/// @param scale
+///     `pos` will be multiplied by this value before computing the color value.
+///     E.g., a scale of 10 will draw 10 lines for each whole-number increment
+///     on the X and Z axes of `pos`.
+/// @param depth_min, depth_max
+///     Controls the opacity of the grid lines relative to the camera depth.
+///     These will be mapped to 0-1 and multiplied by the color value to produce
+///     the final output.
 fn grid_lines(pos: vec4<f32>, depth: f32, scale: f32, depth_min: f32, depth_max: f32) -> f32 {
     let ref_coords = abs(pos) * scale;