UI controls for drawing a hex grid in 3D view

Coding Python Support
1

I am hoping to render a hex grid in the 3d view-port. I’ve found the gpu module, and I’ve figured out how to add controls for this functionality to the overlay panel in the gui.

I can draw the hex grid no problem using something like:

bpy.types.SpaceView3D.draw_handler_add(draw_hex_grid, (), 'WINDOW', 'POST_VIEW')

My hope is to control whether I draw the grid using a checkbox the overlay panel in the UI; however, I am stuck on how I should handle the draw handle and toggling this functionality.

My first attempt is as follows:

def draw_hex_grid(self, context):
    pass

class HexGridOverlayProperties(bpy.types.PropertyGroup):
    """Settings and properties of hex grid overlay"""
    draw_hex_grid: bpy.props.BoolProperty(
        name = "Hex Grid",
        default=False,
        update=toggle_hex_grid
    )
    _handle_hex_grid = None

def toggle_hex_grid(self, context):
    if self.get('draw_hex_grid'):
        self._handle_hex_grid = bpy.types.SpaceView3D.draw_handler_add(draw_hex_grid, (self, context), 'WINDOW', 'POST_VIEW')
        print(self._handle_hex_grid)
    elif self._handle_hex_grid is not None:
        print(self._handle_hex_grid)
        bpy.types.SpaceView3D.draw_handler_remove(self._handle_hex_grid, 'WINDOW')
    else:
        print('No Handle', self._handle_hex_grid)

I always get No Handle on the console when un-checking the box, which to me implies that I can’t track extra state this way in a PropertyGroup. This makes some sense as I do feel I’ve gone a bit off the beaten track here.

Has anyone tried something like this before and have any advice on what I should do?

I want to add an operator for snapping vertices to the grid, I imagine the way to go would be using a ModalOperator, but I don’t get the feeling that would be the appropriate way to have the grid just render all the time when toggled in UI.

2

You can see this script for drawing using the modal operator:
\blender\4.2\scripts\templates_py\operator_modal_draw.py
This is much more standard way to draw stuff, because it will allow you to create draw handlers on activating the operator and deleting the handler when operator gets finished.

And about the hexagons something like this:

https://www.redblobgames.com/grids/hexagons/

3

I’m fine with the hexagons, I do intend to add modal operators for snapping to the grid, but I saw somewhere that modal operators prevent autosaving, if so it’s not really appropriate for drawing a hex grid 100% of the time when blender is open.