# Viewshed

The **Viewshed** tool in SiEGA allows users to visualize line-of-sight coverage from a specific point in a 3D environment. By placing a "viewshed actor" into the scene, users can see which areas are visible or obstructed from that vantage point, making it useful for applications like urban planning, surveillance positioning, and visibility testing in city models. The tool is interactive, real-time, and highly customizable, enabling control over field of view, distance, orientation, and resolution.

### Controls

When entering viewshed mode, a new version of fly mode is enabled. Moreover, movement will be facilitated through the WASD controls. 

**W:** Forward\
**A:** Left\
**S:** Back \
**D:** Back

**NOTE:** No other mode (i.e. walk mode) can be enabled during viewshed mode. These modes will be disabled until viewshed mode is deactivated.

### How To Use

To activate Viewshed Mode, open the **Actions** menu and click the **Viewshed** button. Once activated, movement controls switch to *WASD* keys for navigation, and **left-click + drag** lets you pan the camera. This changes the user interaction mode to better support precise placement and manipulation of the viewshed actor.

<figure><img src="/files/Dd6pYjgypjJ0BMXoyYNc" alt=""><figcaption></figcaption></figure>

After enabling Viewshed Mode, a configuration panel appears on the right side of the screen. To begin, click **“Place a Viewshed Actor”** to spawn the interactive object that determines the center point of your visibility analysis. This actor will define the origin of the viewshed.

<figure><img src="/files/0RxxsEeePMYAJ5QDvo0S" alt=""><figcaption></figcaption></figure>

Once the button is clicked, a **blue crystal-shaped actor** will attach to your cursor. Move your cursor to the desired location in the scene, then **click once** to place it. This actor serves as the origin point for calculating visibility.

<figure><img src="/files/UWUtxhuKLQUV3dl5uRso" alt=""><figcaption></figcaption></figure>

After placing the actor, **drag your mouse** to define the initial extent of the viewshed. The distance you drag will determine how far the field of visibility will project from the actor’s location.

<figure><img src="/files/KpPbzhDp9hJVdOhp9PUA" alt=""><figcaption></figcaption></figure>

With the actor in place, you can fine-tune the viewshed field using the sliders on the right panel:

* **Field of View**: Controls the horizontal angle of visibility.
* **Max Distance**: Defines how far the viewshed extends from the origin.
* **Ratio**: Adjusts the vertical compression or expansion of the view cone.
* **View Height**: Raises or lowers the actor's origin point.
* **Yaw**: Rotates the viewshed horizontally.
* **Pitch**: Adjusts the vertical angle.
* **Resolution**: Sets the precision and quality of the viewshed visualization.

<figure><img src="/files/LaRn0T1IllgFT0Ii7kVl" alt=""><figcaption></figcaption></figure>

To reposition the viewshed actor, simply click **“Place a Viewshed Actor”** again. This will remove the current actor and attach a new one to your cursor, allowing you to place it at a new location.

<figure><img src="/files/OWzfz7oRHqiB8JyKK7bU" alt=""><figcaption></figcaption></figure>

To exit Viewshed Mode, click the **“X” button** at the top of the configuration panel. This will close the panel and return the camera to **fly mode**, restoring normal navigation controls and disabling the visibility overlays.

<figure><img src="/files/WNpMErGIDsVDd5nc1EzX" alt=""><figcaption></figcaption></figure>


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