Custom heatmaps

Performance and capability improvements of computer devices that provide digital images of heatmap visualizations for datasets are provided via both systems and methods. A value-color spectrum is correlated to the dataset via a multi-pass rendering. The multi-pass rendering yields a two-channel mask, which is applied to a map to show the dataset in a heatmap visualization on that map, and may be continually used as the map is manipulated by a user. User interface tools are also provided to enable a user to specify a custom value-color spectrum, how the dataset is to be aggregated, the area of effect for a data point in the visualization, the strength of effect for a data point in the visualization, and which specifies how a dataset will be visually represented in a heatmap.