How to draw (heat map) something on arbitrary meshes using dynamic texture on the exact point I clicked?

Questions
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2

prologue ------------------
My code was inspired by a post here: Drawing on a Dynamic Texture over existing image .
I tried to simplify it a little bit to: https://www.babylonjs-playground.com/#T100FS#105 (here it works fine, that’s the effect I wanna have; you click on the plane and it draws heat map).