Useful to finetune a 
                    XR - Color Calibration
                    Blend perfectly the walls colors with the virtual surrounding.
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                    , it uses the angle between a Stage display and a Camera to smooth a layer or a modifier.
        
 
                    
                    
                                Keep in mind that the selected display on which you will base your display angle mask can be different of the targeted display of the modifier or layer.
          
                                For example: If you are trying to reduce the light incidence on a Led screen, it can be interesting to apply a modifier that reduce the light on the other screen(s) instead of working directly on the impacted one and applying a display angle mask relatively to the impacted one.