Thanks Topi.

Just a quickie today. Another older idea re-done with extra eye candy.

Hexagon grid with values from an underlying raster with a shapeburst fill that changes distance.

I showed this at the annual meeting of the swiss user group in June 2019 and promptly forgot to post it for everyone to see. Let’s blame the scenery?

Have a raster.

Processing -> Create Grid, covering it with points in a spacing of your choice. Use the same CRS as your raster (unless you want to figure out expression-based geometry transformations on your own, like in my elevation lines code)

Change the Symbol layer type to Geometry Generator and enter

with_variable(
  'radius',
  3333,
  buffer($geometry, @radius, 16)
)

where radius should be a value about one third of your spacing.

You should see circles!

For the fill color use this expression and adjust the name of your raster layer:

with_variable(
    'raster_layer',
    'DHM200.xyz',
    ramp_color('Blues',  -- change to an other named ramp here if you like
        scale_linear(
            raster_value(
                @raster_layer, 1, 
                centroid($geometry)  -- back to our point
            ),
            raster_statistic(
                @raster_layer, 1, 
                'min'
            ),
            raster_statistic(
                @raster_layer, 1, 
                'max'
            ),
            0, 1  -- new scale as color ramps go 0 to 1
        )
    )
)

This will get the raster value below our grid point and fit it onto a color ramp between the min and max of all the raster values.

For the stroke use the same expression but wrap darker(..., 150) around it so you get a darker color.

Using Draw Effects add a small Drop Shadow to your circles. I used an offset of 0.5 mm and a blur radius of 1 mm.

Now add another Geometry Generator symbol layer below your existing one and use the following expression:

bounds(buffer($geometry, 5000))

with_variable(
  'radius',
  5000,
  bounds(
    buffer($geometry, @radius)
  )
)

with the radius being half your grid spacing.

Use the same expressions for the colors as above but set the darker value to 200.

For some more fanciness maybe add a “QGIS” text on top of the nupsies?

Exercise: Make it so that the result perfectly covers the raster, instead of being one grid cell off like mine.

Thanks Topi.

Note: You need the current master build of QGIS or wait for QGIS 3.10. I’m a cool kid.

Load a raster layer in QGIS.

Add a new Scratch Layer of Polygon type (in any CRS). Set its Symbology to Inverted Polygons. Use a Geometry Generator as symbol layer type. Set it to LineString/MultiLineString. Enter the expression below and adjust the layer ID (best enter the expression editor and find it in the “layers” tree). Then adjust the scaling factor at the very bottom.

-- UPPER CASE comments below are where you can change things

with_variable(
	'raster_layer',
	'long_and_complicated_layer_id',  -- RASTER LAYER to sample from
	-- this collects all the linestrings generated below into one multilinestring
	collect_geometries(
		-- a loop for each y value of the grid
		array_foreach(
			-- array_foreach loops over all elements of the series generated below
			-- which is a range of numbers from the bottom to the top of y values
			-- of the map canvas extent coordinates.
			-- the result will be an array of linestrings
			generate_series(
				y(@map_extent_center)-(@map_extent_height/2), -- bottom y
				y(@map_extent_center)+(@map_extent_height/2),  -- top y
				@map_extent_height/50  -- stepsize -> HOW MANY LINES
			),
			
			-- we want to enter another loop so we assign the name 'y' to
			-- the current element of the array_foreach loop
			with_variable(
				'y',
				@element,
				
				-- now we are ready to generate the line for this y value
				make_line(
					-- another loop, this time for the x values. same logic as before
					-- the result will be an array of points
					array_foreach(
						generate_series(
							x(@map_extent_center)-(@map_extent_width/2), -- left x
							x(@map_extent_center)+(@map_extent_width/2),  -- right x
							@map_extent_width/50  -- stepsize -> HOW MANY POINTS PER LINE
						),
						-- and here we create each point of the line
						make_point(
							@element,  -- the current value from the loop over the x value range
							@y  -- the y value from the outer loop
							+   -- will get an additional offset to generate the effect
							-- we look for values at _this point_ in the raster, and since
							-- the raster might not have any value here, we must use coalesce
							-- to use a replacement value in those cases
							coalesce(  -- coalesce to catch raster null values
								raster_value(
									@raster_layer,
									1,  -- band 1, *snore*
									-- to look up the raster value we need to look in the right position
									-- so we make a sampling point in the same CRS as the raster layer
									transform( 
										make_point(@element, @y),
										@map_crs,
										layer_property(@raster_layer,'crs')
									)
								),
								0  -- coalesce 0 if raster_value gave null
							-- here is where we set the scaling factor for the raster -> y values
							-- if things are weird, set it to 0 and try small multiplications or divisions
							-- to see what happens.
							-- for metric systems you will want to multiply
							-- for geographic coordinates you will want to divide
							)*10  -- user-defined factor for VERTICAL EXAGGERATION
						)
					)
				)
			)
		)
	)
)  -- wee

If you don’t have your raster data on a SSD this can be a bit slow.

Yes, this works if you change your CRS!