It’s worked out!
Thanks again for your patience!
I still had to add WorldMatrix in Technique / WorldParameters and copy position = inPosition in * .vert so that I can calculate the world position g_WorldMatrix * vec4 (position, 1.0).
In video: The red marking is a parallel projection 0, -1,0.
On steeper slopes you can see the stretch (just to show the difference).
The turquoise marking is the radial solution.
White occurs on flat planes when they overlap.
