SDM Gradient Heatmap

The SDM Gradient Heatmap renders a smooth, continuous color surface from a sparse set of XY sample points. Unlike tile-based heatmaps, values between samples are interpolated — the visual fills the entire plot area with a gradient rather than discrete colored cells.

Key features:

• Smooth interpolation: three algorithms (IDW, RBF, Bilinear) to control how the surface is estimated between samples
• Color presets: Viridis, Turbo, Red-Yellow-Blue, Spectral, or fully custom min/mid/max colors
• Isolines: contour lines at evenly-spaced value thresholds, with optional floating labels
• Sample point markers: six shapes, configurable size, heatmap-derived or fixed colors
• Category labels: smart multi-pass placement with leader lines, clustering, and word wrap
• Axes: X and Y axes with optional titles and manual range control
• Legend: gradient color bar with auto-formatted tick labels (Right, Left, or Bottom)
• Cross-filtering: click or Ctrl+click sample points to filter other visuals
• Tooltips: X, Y, Value, Category, and custom tooltip measures on hover

The visual supports cross-filtering, rich tooltips, and is designed for spatial analysis, scientific visualization, and enterprise dashboards where continuous data surfaces matter.

Documentation: https://socio-data-management.github.io/sdmpbigraph-docs/