Feat: Per-point custom colors

[vincentjzy]

Closes #144

This PR expands the function of PlotSurface. It allows an additional series of data as input. The value could be used to indicate the property at each point in the 3D point cloud, such as temperature, density, potential, etc. This function seems to be required in a wide variety of scientific figures.

The example DemoSurfacePlots in implot3d_demo.cpp is modified to show the effect (see the animation below). The existing plot functionality is unaffected.

DemoSurfacePlots

It is noteworthy that there are quite a few codes in this modification duplicated from the original PlotSurface. I will be very happy if the maintainer could consider to merge the modification into PlotSurface in a more elegant way.

Please let me know if there is any comment or suggestion.

[brenocq]

Hi! Sorry for taking so long to reply. Thank you for creating the PR!

It sounds super useful to be able to specify a different color for each point (also being able to specify a different colormap value for each point). I'll review the code in the following days.

I've just tested your demo, very nice color function hahah loved it

I also found some PRs/Issues in ImPlot that may be interesting for us: epezent/implot#608 epezent/implot#332 epezent/implot#298

[brenocq]

I've just created #144 with some ideas for the per-point custom color implementation. It would be nice if you could leave a comment there so I can also add you as an assignee.

Since I kind of just increased the scope of this PR to also implement this feature all other functions, I'm more than happy to help with the coding :)

Let's leave comments in this PR before and after we implement something (GitHub mutex!), so we don't do double work.