recalculating normals in shaders for shadow casting

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:bust_in_silhouette: Asked By Inces

Can someone explain it to me ?
Most of the time when I don’t want special effect to cast shadow I have to manually turn that off in Geometry Instance, because no matter how far I modify VERTEX in shader, it will still cast shadows. But there are times, when I modify VERTEX and normals completely lose it, mesh is prevented from casting shadows.
I know there is a mathematic way to recalculate normals, so the light is handled correctly. But actually I wish for the other thing - how do I annihilate normals in shader, so the light is not handled at all, and no shadows are cast ??? There is a bug with Gridmap, that disables turning shadows off in manual way and I really need to bypass it.