How to achieve the red shadow on the map border and the blue shadow on the top line as shown in the figure?

[HappyFroggy]

I’m learning Three.js and want to develop a 3D map component. I need to implement a shadow effect like the one shown in the picture, but I don’t know how to do it. What kind of knowledge do I need?

[towrabbit]

Why not draw a half transparent picture and use it as texture..