How to Use Heightscale Map

Hey, I am currently trying to create a terrain based off of a height map I got from tangrams, the only thing is I keep getting told that the format is RGBA and not Gray. I've been trying to figure it out and nothing I look up really helps at all

I think you need to save the height map image as a Grayscale image, instead of an image file that contains the default RGBA channels. In the Core terrain tutorial VOD (Building immersive video game worlds in Core using terrain tools) on YouTube I believe they use Photoshop to do this. I'm not sure what other programs there are that can also be used to do this, in case you don't have PS. Hope this helps!