> For the complete documentation index, see [llms.txt](https://docs.imerit.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.imerit.net/3d-multi-sensor-fusion/labeling/3d-multi-sensor-fusion-labeling-editor/key-features/hotzone.md).
# Hotzone
Hotzone lets annotators cut out a region of the point cloud and work inside it on its own. Points outside the boundary are hidden and protected from segmentation, so no drawing tool can label them by accident. Because only the isolated region is active, rendering, Merged Point Cloud (MPC), and playback all run on a much smaller point set.
{% hint style="success" icon="lightbulb-on" %}
This feature is used to help focus on a specific area. The isolation is applied across the frames on the same area.
{% endhint %}
The Hotzone includes:
* **Boundary drawing in BEV or 3D:** Place vertices by clicking, trace freehand with the lasso, or combine both in one boundary.
* **World-anchored boundary:** The hotzone stays fixed to the same real-world location as you move through frames, for the rest of your session.
* **Segmentation protection:** Points outside the boundary, and points inside it that are hidden by the ground or ceiling filters, cannot be segmented by any drawing tool, locked or unlocked.
* **Scoped MPC and playback:** Merged Point Cloud and playback process only the points inside the hotzone that pass the active filters.
* **Filters during setup:** The ground/non-ground/all points filter and the Ground & Ceiling Mover stay available while you position and draw.
***
## Use Cases
* **Dense or cluttered scenes:** Isolate an intersection, parking area, or construction zone so surrounding points don't get in the way while labeling.
* **Irregular regions:** Use the freehand lasso to cut out vegetation, terrain, or curb edges that are slow to outline vertex by vertex.
* **Static object segmentation:** Turn on MPC inside the hotzone to see poles, signs, barriers, and buildings at higher density without merging the whole sequence.
* **Objects at region edges:** Place a Cuboid or 3D Polygon that crosses the boundary without capturing points outside the area you meant to label.
* **Ground and overhead clutter:** Combine the hotzone with the ground filter or ceiling slider so hidden ground or overhead points cannot be segmented by mistake.
* **Fast sequence review:** Play back only the isolated area to check tracking and segmentation consistency across frames.
***
## Benefits
* **For Annotators:** Less visual clutter and smoother rendering in the work area, with no risk of segmenting points outside it. The boundary persists across frames, so it is drawn once per session instead of once per frame, reducing time per annotation in dense scenes.
* **For Reviewers:** Scoped playback loads faster, so a region can be checked across the full sequence without waiting on the entire point cloud.
* **For Customers (AI/ML & Perception Engineering):** Fewer stray labels on background, ground, or overhead points means cleaner segmentation and more reliable delivered datasets.
* **Cost Efficiency:** Fewer accidental labels reaching QA reduces rework hours, and scoped MPC lowers the processing load on large sequences.
***
## Steps to use Hotzone
{% stepper %}
{% step %}
### Create a Hotzone
1. **Turn on Hotzone:** Click the Hotzone toggle in the header. The cut-out polygon tool activates right away, and the annotation drawing tools stay disabled until the hotzone is complete.
2. **Choose the drawing mode:** Select **BEV** or **3D** from the selector in the header.
3. **Position the camera:** Use **Spacebar** to pan, zoom, and rotate until the area you want is in view. You can also adjust the ground/non-ground/all points filter or the Ground & Ceiling Mover to clear clutter.
4. **Draw the boundary:** Left-click to place each vertex. Two preview lines follow the cursor, one from the last vertex and one from the first, showing how the shape will close.
* To trace freehand, press **G** to turn on the lasso and move the cursor along the edge. Press **G** again to return to click-to-place; your progress is kept.
* To start over, press **Esc**. All placed vertices are discarded.
5. **Complete the boundary:** Right-click. The shape closes automatically, points outside it are hidden, and camera navigation and annotation tools are enabled again.
{% endstep %}
{% step %}
### Work Inside the Hotzone
1. **Annotate:** Use Cuboid, 3D Polygon, 3D Polyline, or Brush as usual. Only points that are inside the boundary and currently visible are segmented. The annotation details pop-up still appears, even if part of the annotation sits outside the boundary.
2. **Move through frames:** The hotzone stays in place as you navigate the sequence, anchored to the same real-world location.
3. **Use Merged Point Cloud:** Turn MPC on to merge only the points inside the hotzone that pass the active filters. Static objects in the area appear denser.
4. **Play back the sequence:** Start playback to render only the points inside the hotzone, for a faster review.
{% endstep %}
{% step %}
### Disable the Hotzone
1. Click the Hotzone toggle in the header to turn it off.
2. All hidden points and annotations reappear, the boundary is cleared, and MPC and playback return to the full sequence. You can now create a new hotzone
{% endstep %}
{% endstepper %}
### Keyboard Shortcuts
| Pan, zoom, and rotate before drawing | **Spacebar** |
| ------------------------------------ | --------------- |
| Place a vertex | **Left-click** |
| Turn freehand lasso on or off | **G** |
| Discard the boundary and restart | **Esc** |
| Complete the boundary | **Right-click** |
## Best Practices
* **Frame first, then draw:** Get the camera angle right with **Spacebar** before placing the first vertex. Camera navigation is locked while you draw.
* **Clear clutter before drawing:** Adjust the ground filter or ceiling slider first, so the edges you trace are easy to see. Changing a filter mid-draw does not move vertices you have already placed.
* **Mix lasso and clicks:** Use the lasso for organic edges like vegetation, and switch back to clicks for straight edges like curbs and walls.
* **Leave a small margin:** Draw the boundary slightly wider than the objects you want to label. Points outside the boundary cannot be segmented, so a tight boundary can clip the edge of an object.
* **Check for empty annotations:** An annotation placed entirely outside the boundary, or over hidden points only, ends up with zero segmented points and is treated as invalid.
* **Expect thinning in later frames:** As the ego vehicle moves away from the hotzone, points inside it can thin out or disappear. This is expected behavior, not a defect.
* **Redraw after a reload:** A hotzone lasts only for your current session. Reloading the page or logging out clears it, and other users on the task never see it.
* **Datasets without egopose:** The hotzone boundary does not carry over to other frames when the dataset has no egopose data.
* **Undo does not cover Hotzone:** **Ctrl+Z** and **Ctrl+Shift+Z** do not undo enabling, creating, or disabling a hotzone. Use **Esc** while drawing, or toggle Hotzone off to start again.
---
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