three.js is quite well suited to things like terrain generation. There's actually an example in the official docs - https://threejs.org/examples/webgl_terrain_dynamic.html - it wouldn't take much effort to swap out the noise generator for a heightmap.

Webdev kneejerk reaction I guess, haha.

Everything is web nowadays! Kudos for making a standalone application.

C# and its world might as well be a foreign language to some here...

Lol, my apologies I misunderstood the title :-D