In my use-case I need to be able to display a 3rd dimension in a scatter plot. I'm about to jump into QCP source-code to implement this functionality, but since this forum has been a great source of information over time, I thought I should begin by asking here for pointers.

Conceptually the behaviour is similar to a ColorMap, where the cells contain the z-axis values, and their colour is derived from a gradient controlled by a ColorScale. However, unlike a ColorMap which displays a grid of cells, this graph should display a scatter of points, where the marker colour is derived from the z-axis values.

My use-case is limited to a scatter plot, but it strikes me that the functionality to display 3-dimensional data could be usefully generalised to other graph types too (eg. lines, bars, etc..). Does anybody have any insights they could share on the optimal approach for implementing this?

I am considering my starting point to be adding an optional 3rd axis to QCPGraphData and porting the functionality from ColorMap to QCPGraph, so that it's possible to attach a ColorScale. Does anyone have any additional insight?