Custom value range for colormaps

[HeresJ0nny]

Hello.
I'm currently using PlotSurface with a custom colormap (red, white, green). The range of values for the data I'm plotting is always between -1 and +1 but any given batch of data may not actually contain both extreme values of -1 and +1.
Right now the colormap uses the min and max values of the given data batch to determine its interpolation. This means that if my data in a given batch happens to fall between -1 and +0.5 then the value that gets mapped to white is -0.25 instead of +0.0.
I want the value 0 to always map to white though. So I would like to be able to set a min and max value of -1 and +1.

Kind regards.

[brenocq]

Hi @HeresJ0nny! I took the liberty to convert your issue into a discussion to better organize feature requests.

This is actually a feature I had planned to implement in the future, so thank you for letting me know it’s something you need! I’ll prioritize it in my roadmap and aim to have it implemented within the next few days.

If anyone else is interested in contributing to this feature, please let me know — help is always welcome! :)

[brenocq]

I'm moving this task to high priority since it is getting more up votes.

[brenocq]

@HeresJ0nny now it is possible to set custom value ranges for colormaps! This feature is in dev and can already be tested (commit 5fe6144). It will be merged into main with the release v0.2!

Peek.2024-12-25.17-09.mp4

The ImPlot3D::PlotSurface API was changed slightly to support this feature (added scale_min and scale_max arguments):

IMPLOT3D_TMP void PlotSurface(const char* label_id, const T* xs, const T* ys, const T* zs, int x_count, int y_count, double scale_min = 0.0, double scale_max = 0.0, ImPlot3DSurfaceFlags flags = 0, int offset = 0, int stride = sizeof(T));

I tried to follow the same API as the ImPlot::PlotHeatmap:

IMPLOT_TMP void PlotHeatmap(const char* label_id, const T* values, int rows, int cols, double scale_min=0, double scale_max=0, const char* label_fmt="%.1f", const ImPlotPoint& bounds_min=ImPlotPoint(0,0), const ImPlotPoint& bounds_max=ImPlotPoint(1,1), ImPlotHeatmapFlags flags=0);

Let me know if you guys have any problems while testing it! Feel free to share a video of your surface plot in our gallery, I would love to see it :)