Text and image labels in TerraExplorer, whether created as objects or as points or annotations in feature layers, enable you to display text and symbols on the terrain. Properly configuring their visibility settings ensures that labels are clearly visible at the right zoom level, while avoiding clutter and overlap when viewing large or dense datasets.
This article explains how label visibility works, and how scaling modes affect their behavior.
Key visibility principles:
- Use Max Visibility Distance to define when labels disappear based on distance (3D radius)
- Use Min Visibility Height to hide labels when flying too low (camera height only)
- Choose the correct scaling mode depending on whether labels should remain readable at all zoom levels or behave like real-world objects
- Adjust values carefully to avoid clutter, especially in dense datasets
By combining these settings, you can create clear, readable, and professional label displays in your TerraExplorer project.
Label Scaling Modes
Text and image labels support two scaling modes that determine how their size behaves relative to the camera.
Fixed Pixel Size
Keeps the label size constant in screen pixels, regardless of zoom level.
- The label appears the same size whether you are zoomed in or out.
- Visibility is controlled primarily using Max Visibility Distance.
Recommended use: Icons, or text labels that must remain readable at all zoom levels.
Fixed Real-World Size
Keeps the label size constant in real-world units.
- The label appears smaller when zooming out and larger when zooming in.
- Scale can be adjusted using the Scale property (see below).
Recommended use: Labels that should behave like real objects in the 3D world.
Visibility Settings
To control when a label appears or disappears, two key properties are used:
Max Visibility Distance
Defines the maximum distance between the camera and the label at which the label is visible.
- The label disappears when the camera moves farther away than this value.
- This is calculated as a 3D distance (radius) between the camera and the label’s pivot point.
Note: This is not based on camera height, but on the actual distance from the camera to the label.
Example:
- Max Visibility Distance = 30,000 m
- Label altitude = 500 m
If the camera is directly above the label, the label disappears at 30,500 m above ground. If the camera is at an angle, the label disappears once the straight-line distance exceeds 30,000 m. Think of this as a sphere around the label - once the camera moves outside the sphere, the label disappears.
Min Visibility Height
Defines the minimum camera height (altitude) at which the label is visible.
- The label disappears when the camera is below this height.
Key Difference
Understanding this distinction is essential for correctly controlling label visibility:
| Property | Based On | Behavior |
| Max Visibility Distance | Distance from camera to label | Radius-based visibility |
| Min Visibility Height | Camera height only | Hides labels when flying low |
Improving Label Readability (Best Practices)
When working with large datasets (e.g., street names, city labels, or electricity poles), labels can quickly become crowded.
Use Max Visibility Distance to Reduce Clutter
Set a shorter Max Visibility Distance to:
- Prevent too many labels from appearing when zoomed out
- Avoid overlapping labels
Example:
- Street names → use short distances so distant horizon views remain clean.
- City labels → use Field by Attribute to classify the cities visibility based on the city population size, so labels only appear when zoomed in.
Use Min Visibility Height to Control Horizon Clutter
Set a Min Visibility Height to:
- Hide labels when the camera is too low
- Prevent excessive labels when viewing the scene from a shallow angle
This is especially useful when looking toward the horizon or viewing dense urban datasets
Scale Property
When using Fixed Real-World Size, you can control label size using the Scale property.
- Defines the label size in meters per pixel
- Affects the overall size in addition to font size (for text labels)
Note: Scale is only available when using Fixed Real-World Size
Image Labels vs. Text Labels
The same visibility principles apply to text labels and image labels, with a few differences:
Shared Behavior
- Both use:
- Fixed Pixel Size
- Fixed Real-World Size
- Min Visibility Height
- Max Visibility Distance
Image Label Differences
- No font size (size is based on the image itself)
- Fixed Pixel Size keeps the image at its original screen size regardless of zoom
- Fixed Real-World Size uses the image’s original pixel size as a base and can be scaled using the Scale property