QGIS Geometry Generator expression to approximate rock outcroppings

gistfile1.txt

with_variable(
	'segment_len',
	11, -- the length of each segment
	collect_geometries(
		array_foreach(
			generate_series(
				0, length(boundary($geometry)) - @segment_len, @segment_len
			),
			with_variable('offset_inner',
				offset_curve(
					make_line(
						line_interpolate_point(boundary($geometry), @element),
						line_interpolate_point(boundary($geometry), @element + @segment_len)
					),
					rand(1,11), -- range offset of the inner boundaries
					1
				),
				with_variable('offset_outer',
					offset_curve(
						make_line(
							line_interpolate_point(boundary($geometry), @element),
							line_interpolate_point(boundary($geometry), @element + @segment_len)
						),
						rand(12,30), -- range offset of the outer boundaries
						1
					),
					collect_geometries(
						@offset_outer,
						make_line(
							start_point(@offset_inner),
							start_point(@offset_outer)
						),
						make_line(
							end_point(@offset_inner),
							end_point(@offset_outer)
						)
					)
				)
			)
		)
	)
)

Been looking in to this again recently; and can't get this to render anything with the LINZ rock data in QGIS 3.2.3. Other than changing the geometry type to linestring is there something else I'm missing?

Hi Jake, it still seems to work for me. You do need to set the output to Geometry Type to "LineString" though.

Example:

I get an expression error:

Update: It was my version of QGIS in the end. Upgraded to 3.14 (I wish they'd use leading zeros) and it worked without issue. Thanks!