What low bloody tools or libraries can visualize a heat map?

Question

infographics

Firstly, a heat map, in cases of a not very smooth function (built on the result of rather 'noisy' experiments) is not too 'visual' (but for now, you still have to look with your eyes), it looks something like this:

spoiler

Microsoft excell has a beautiful 3d implementation and its main 2d variation is a surface diagram:

spoiler

But there are no available options for customizing it, i.e. at least you can’t define your own color scheme and levels (so that they are common to several charts), plus using excell is not very convenient, I would like a command line utility or library.
I can roughly imagine how excel works with these charts (we divide the cell into 2 triangles, we take the gradient based on the values ​​​​at the vertices, if there are boundary values ​​\u200b\u200bfrom the legend on the edges, we divide them by a segment whose ends are equal to these boundary values ​​​​(then the contours will be visible ).
Moreover, it is very expensive to build a complete result matrix (inefficient in terms of resources), for example, for some values ​​(areas on a heat map) the number of points is much larger (in places of strong changes), but the classical heat map does not allow them to be used, since it needs to the points were evenly spaced from each other (of course, you can generate a table with cells for points located far from each other, but this is not very efficient when displaying, and does not improve visibility, even Excel surfaces stop 'working').
Are there any ready-made tools / algorithms that allow using a set of points (x, y coordinates and z level) to build a triangulation (vertices - points) and color the triangles accordingly?
In the tutorials on oppengl shaders, the very first example paints them properly, so from the point of view of implementation, I don’t think there will be problems (cut out points that are too close, build a triangulation of the same dilon and draw with opengl shaders), I just thought, suddenly there is already a ready-made tool .

spoiler

I watched gnuplot, my task is solved there not very trivially, maybe there are some libraries for javascript html5 charts, there are very functional and beautiful ones, in my case it’s suitable, anyway, the interface for working with data mostly works in the browser, it’s even good if the generation will be in it.