I made some 3d audio Spectrograms using Babylon.js and Audacity sound editor. The tutorial for these is here together with the HTML, textures and sound files.
An Audacity user noticed that they had all stopped working and traced the problem to this line:
var ground = BABYLON.Mesh.CreateGroundFromHeightMap("ground", heightmap, 500, 264, 1000, 40, -40, scene, false);
Note that the minimum height of 40 is larger than the maximum height of -40. This is because the grayscale height texture has darker shades = higher elevations. However, it worked fine for several models back in March 2018.
He managed to get the model working by swapping the minimum and maximum heights and inverting the grayscale texture. The model fails if minimum is larger than maximum height.
Is this a permanent change or a glitch that slipped thru? Sorry that I can’t tell you exactly when it changed except it was some time after 12mar18.