What an AoI does
An Area of Interest (AoI) is a polygon you draw around part of a drawing to say "only count inside here". With one or more AoIs on a drawing:
- Symbol detection is restricted to them. Both Auto Count Symbol and Auto Detect Symbols discard any match whose centre falls outside every AoI. This applies whether the drawing is vector or image.
- Auto Takeoff on an image drawing is narrowed to them. On scanned and flattened sheets, the linework detector only looks inside the AoIs.
- They were the input to the older legend flow. Drawings set up under the original Stage 1 pipeline had AoIs drawn first and the legend read within them. See Legend-based auto-detection.
Two things AoIs are commonly confused with:
- An AoI filters detection before it runs. A zone groups markers after they have been placed, and splits the counts in the export. See AoIs and zones compared.
- An AoI is not a legend. A legend rectangle marks the symbol key so it can be read; an AoI marks the area to be counted.
An AoI keeps working when it is hidden. Hiding only stops it being drawn on the canvas — detection still stays inside it. If counts stop appearing where you expect, check whether an AoI is still on the drawing.
Where the controls are
In the sidebar, above the marker list, click the AoIs, Legends & Zones button. The AoIs section is at the top of the dropdown.
| Control | What it does |
|---|---|
| Lock AoIs / Unlock AoIs | Stops AoIs being dragged, resized or deleted. |
| Hide AoIs / Show AoIs | Draws the polygons on the canvas or takes them off it. |
| AoI templates | Import, create or update a reusable set of AoIs. See AoI templates. |
| New | Create new AoI — arms the drawing tool and closes the menu. |
Each AoI you draw is listed below with a colour swatch, its name and a delete button. The list reads No AoIs until you draw one.
Drawing an AoI
An AoI is a polygon, so you click its corners rather than dragging a box.
- 1
Open AoIs, Legends & Zones and click New in the AoIs section. The cursor becomes a crosshair.
- 2
Hold CTRL (CMD on a Mac) and click each corner of the area in turn. Without the key held, dragging pans the drawing instead.
- 3
Right-click to close the shape. The AoI is filled in your AoI colour and appears in the list.
As soon as an AoI is committed, ZeroCount locks the whole set and tells you: AoIs have been automatically locked. That stops a corner being dragged out of place while you work. Use Unlock AoIs if you need to adjust one.
To abandon a shape part-way through, press Esc or click the Current Tool button in the header.
Renaming, recolouring and deleting
- Rename — click the AoI's name in the list and type. Enter commits, Esc reverts.
- Recolour — click the colour swatch at the left of the row and pick a colour, then Apply.
- Delete — click on the row. While AoIs are locked the button is greyed and hovering it says Unlock AoIs before deleting.
Auto hide AoIs
Once your AoIs are set, they are usually in the way. Auto hide AoIs is on by default and takes care of that: the first time you start any takeoff on a drawing that has AoIs, ZeroCount locks and hides them and shows a message reading AoIs have automatically been locked and hidden while you continue with your takeoff.
The AoIs are still there and still restricting detection — they are just no longer painted over the drawing.
To change the setting, open the user menu and choose User Preferences , then Canvas › On-canvas Items › Auto hide AoIs. Turning it off leaves the polygons visible while you count.
Changing the default AoI colour
Open User Preferences › Appearance › Marker Colours and set AoI Colour. The default is green.
This is the colour new AoIs are drawn in on every drawing. Changing it also recolours the AoIs already on the drawing you have open, so you can use it to lift AoIs off a busy sheet.
When not to use an AoI
AoIs earn their keep on a sheet with several plans on it, or where the title block and notes keep producing false matches. On a straightforward single-plan drawing they mostly add a step, and an AoI you forget about becomes a silent reason for missing counts later.
If counts are coming back low and you are not sure why, open AoIs, Legends & Zones and check the list. An empty list rules AoIs out entirely.
Next steps
- Detect New Symbol — count a symbol once the area is set.
- Drawing a legend — mark the symbol key so scans read it row by row.
- AoI templates — save a set of AoIs and place them on other drawings.
- AoIs and zones compared — which one to reach for, and why.
- Detection tips — other reasons a count comes back short.