It is nearly perfect but one single step is missing. The texture is projected by an orthographic matrix that goes through the hole scene. This leads to the fact that the hole is cut at all walls that are hit by the matrix. One solution would be to use different meshes and different materials for each wall. But since I want to use just one mesh for all walls it is necessary to adapt the matrix. The matrix has to project the texture from inside to outside. So it is necessary that the texture projection will project from the position vector to the given direction: https://playground.babylonjs.com/#9UU80W#68
I would really like to use this method wherefore I am willing to pay someone who is able to solve this problem.
Please let me know.