How to divide a buffer using geometry generator in QGIS 3.X

Question

Some background and working PostGIS query and Python script available here.

How to split circles in 12 sections in PostGIS?

I don't want to create a new polygon layer out of points. I really like QGIS Geometry generator. My idea is to use QGIS Geometry generator and show this divide buffer as symbol.

Any suggestion?

Answer 1

1) Prepare center points (used as seeds).

• Create your first center point as a point vector layer.
• Duplicate the point so that you have 12 points (in my Windows OS I will hit Ctrl+C to copy the point then hit Ctrl+V eleven (11) times.
• Then create a field to represent the center azimuth of each wedge (e.g. "fid" * 30 - 15 in this example).

2) Start Geometry generator and give: wedge_buffer($geometry, "az", 30, 50)

Sorry#1: I had used Geometry by Expression but you can use Geometry generator.

Sorry#2: The figure shows center azimuth (15, 45, ...345) of each wedge buffer but you would be able to modify it easily.

Answer 2

Great answer by @Kazuhito! An alternative could be to create a buffer on your point layer and then add another geometry generator layer to draw lines to represent the segments The value of 0.1 used in the expressions is the buffer distance, change this for your requirement.

1. Create the buffer using expression:

   buffer($geometry, 0.1, 36)  
   

   

2. Create the lines using expression:

   make_line( 
   make_point( $X + 0.1*cos(radians(0)), $Y + 0.1*sin(radians(0))),
   $geometry,
   make_point( $X + 0.1*cos(radians(30)), $Y + 0.1*sin(radians(30))),
   $geometry,
   make_point( $X + 0.1*cos(radians(60)), $Y + 0.1*sin(radians(60))),
   $geometry,
   make_point( $X + 0.1*cos(radians(90)), $Y + 0.1*sin(radians(90))),
   $geometry,
   make_point( $X + 0.1*cos(radians(120)), $Y + 0.1*sin(radians(120))),
   $geometry,
   make_point( $X + 0.1*cos(radians(150)), $Y + 0.1*sin(radians(150))),
   $geometry,
   make_point( $X + 0.1*cos(radians(180)), $Y + 0.1*sin(radians(180))),
   $geometry,
   make_point( $X + 0.1*cos(radians(210)), $Y + 0.1*sin(radians(210))),
   $geometry,
   make_point( $X + 0.1*cos(radians(240)), $Y + 0.1*sin(radians(240))),
   $geometry,
   make_point( $X + 0.1*cos(radians(270)), $Y + 0.1*sin(radians(270))),
   $geometry,
   make_point( $X + 0.1*cos(radians(300)), $Y + 0.1*sin(radians(300))),
   $geometry,
   make_point( $X + 0.1*cos(radians(330)), $Y + 0.1*sin(radians(330)))
   )
   

   

3. Result: