QGIS Geometry Generators - CartoHack #9

branches.txt

collect_geometries(
	array_foreach(
		generate_series(1, to_int("count"), 1),
		translate(
			geom_from_wkt(
				concat(
					'LINESTRING(0 50,',
					to_string(rand(-25, 25,  concat("fid", '_x', @element))),
					' ',
					to_string(rand(-5, 5,  concat("fid", '_y', @element))),
					')'
				)
			),
			x($geometry),
			y($geometry)
		)
	)
)

leafs.txt

collect_geometries(
	array_foreach(
		generate_series(1, to_int("count"), 1),
		translate(
			translate(
				rotate(
					geom_from_wkt(
			'CURVEPOLYGON(
				COMPOUNDCURVE(
					CIRCULARSTRING(
						0 0, 15 -5, 30 0,
						     15 5, 0 0
					)
				)
			)'
					), rand(-200, 20, concat("fid", '_r', @element)), make_point(0, 0)
				), x($geometry), y($geometry)
			), rand(-25, 25,  concat("fid", '_x', @element) ), rand(-5, 5,  concat("fid", '_y', @element) )
		)
	)
)

qgis_polar_function.py

from qgis.core import *
from qgis.gui import *
import math

@qgsfunction(args='auto', group='Custom')
def polar_point(radius, angle, feature, parent):
    """
    Calculates the polar coordinate from radius and angle (in radians)
    <h2>Example usage:</h2>
    <ul>
      <li>polar_point(5, pi) -> 5</li>
    </ul>
    """
    x = radius * math.cos(angle)
    y = radius * math.sin(angle)
    # point = QgsPoint(x, y)
    return str(x) + ' ' + str(y)

radial_lines.txt

with_variable(
	'radius',
	20,
	collect_geometries(
		array_foreach(
			generate_series(1, "count" * 5, 1),
			translate(
				geom_from_wkt(
					concat(
						'LINESTRING(0 0,',
						polar_point(
							@radius + randf(0, 15),
							pi() * 2 / ("count" * 5) * @element
						),
						')'
					)
				),
				x($geometry),
				y($geometry)
			)
		)
	)
)

raster_values.txt

with_variable(
  'config',
  map(
    'steps_x', 50,
    'steps_y', 50,
    'elevation', 0.0002,
	'raster_layer', 'srtm_germany_dtm'
  ),
  collect_geometries(
    array_foreach(
      generate_series(
        y_min($geometry),
        y_max($geometry),
        (y_max($geometry) - y_min($geometry)) / @config['steps_y']
      ),
      with_variable(
        'cY',
        @element,
        geom_from_wkt(
          concat(
            'LINESTRING(',
            array_to_string(
              array_foreach(
                generate_series(
                  x_min($geometry),
                  x_max($geometry),
                  (x_max($geometry) - x_min($geometry)) / @config['steps_x']
                ),
                concat(
                  to_string(@element),
                  ' ',
                  to_string(
                    @cY + 
                    coalesce(
                      raster_value(
                        @config['raster_layer'],
                        1,
                        make_point(
                          @element,
                          @cY
                        )
                      ),
                      0
                    ) * @config['elevation']
				  )
                )
              ),
              ','
            ),
            ')'
          )
        )
      )
    )
  )
)