Isolines
The Isolines card adds contour lines to the heatmap surface — curves that connect all points of equal interpolated value, similar to elevation contours on a topographic map.
Visibility
| Property | Description | Default |
|---|---|---|
| Show | Show or hide all contour lines | Off |
Line Appearance
| Property | Description | Default |
|---|---|---|
| Count | Number of isolines, distributed evenly across the value range | 8 |
| Color | Stroke color of the contour lines | #222222 |
| Width | Stroke width in pixels | 0.8 px |
| Transparency | Opacity of the isoline strokes (0 % = fully opaque) | 30% |
Isoline Labels
| Property | Description | Default |
|---|---|---|
| Show Labels | Display the interpolated value next to each contour line | Off |
When enabled, labels float above the isoline with a lightly translucent background. The label placement engine:
- Avoids overlapping with category label rectangles already on the SVG
- Avoids overlapping with the plot borders
- Spaces labels along each contour at regular intervals
Readable contours
For a clean map-like appearance, set Count to 5–10, Transparency to around 30–40 %, and Width to 0.5–1 px. Enable Show Labels only when exact threshold values matter to the reader — they add noise at high counts.
Isoline positions
Isoline thresholds are evenly spaced between the effective Range Min and Range Max of the Color Scale. Changing the manual range will shift the isoline positions accordingly.