Grid spacing by attributes, QGIS

Question

Is it possible to define point grid spacing by attribute in QGIS?

EDIT: I really dunno is this even possible. Added a picture where I try to demonstrate the situation.

So the problem is that I want to generate a grid where I can create a grid that takes the spacing value from an attribute table like the one below. And also that the grid is only placed inside the polygons. Normally I do this so that i create a grid and the I select the points that are located inside a specific polygon and delete all the points that are not inside the wanted polygons.

(I'm not very familiar to using the python console, but every answer is welcome.)

Example:

(Simple question, but I didn't find any answers to it.)

Answer 1

I got a processing model to almost do what you want. It creates a grid inside each polygon. Each grid should have its own spacing, as defined by the fields "Horizontal_spacing" and "Vertical_spacing". But the grid spacing is identical for each polygon. Hopefully this will be useful to get you started in the right direction.

---

Create a processing model.

Add one input: Vector feature

Add two algorithms:

1. Create Grid

   grid extent: extent of input feature

   horizontal spacing: pre-calculated value with the expression "Horizontal_Spacing" (the field name of the horizontal spacing field, in double quotes)

   vertical spacing: pre-calculated value with the expression "Vertical_Spacing" (the field name of the horizontal spacing field, in double quotes)

   

2. Clip

   Input layer: 'Grid' from algorithm 'create grid'

   Overlay layer: Input Feature

   

The model looks like this:

Run the model. Click the round green arrow to "iterate over this layer, creating a separate output for every feature in the layer"

Here's the model output:

As you can see, the grid spacing is identical for each polygon. It should have a different spacing for each feature, as defined by the fields "Horizontal_spacing" and "Vertical_spacing."

---

I couldn't figure out how to make this work as intended, but here's a workaround I figured out:

Add 2 Number inputs called Horizontal and Vertical spacing. Use these instead of the field values in the Create Grid algorithm.

Make a list of all unique combinations of vertical and horizontal spacing you have. In my example, that list is {1x1,2x2,3x3}. You'll have to run the model as many times as you have unique combinations.

Before you run the model, use the "select by expression" tool to select features where the horizontal and vertical spacing match the first combination on the list.

Run the model, checking the box for "selected features only." Type in the horizontal and vertical spacing values you used in the "select by expression" tool. The output will be a point grid inside the selected polygons, with horizontal and vertical spacing defined by the values you entered.

Repeat for every unique combination of vertical and horizontal spacing.