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Sunlight shines through backside of helmet and creates highlight on the inside of the front.

Hi guys,
As the title says, I have a problem with a helmet model that sits around the player camera.

The problem: When the player faces away from the sun, the sun reflects on the metallic inside of the helmets front, as if the light passes right through the backside and hits the front.
To simplify the issue, I made a 25cm Sphere in max and gave it an outwards shell thickness of 5 cm and a simple material with metal=1 and rough = 0,1. The sun still goes through it and lights up the front of the
inside of the sphere.
Additionally the normal map details of my material all light up as well if the normal detail faces the sun. It is as if lighting completely ignores the occlusion of the helmet.

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               The light only stops shining through if I make the shell of the sphere <12 cm thick. That is far to thick for a realistic futuristic helmet like the one I´m working with.
               The objects cast regular shadows on the ground and it is darker inside the helmet, so the light does not completely go through, it is just the sun highlight and normal details that get lit as if the helmet had no 
               backside and was just open towards the sun.

               I tried turning off the different lighting components like atmospheric fog, skylight, directionla light, sphere reflection capture etc. The Issue seems not to be related to a single lighting component.

Settings: My directional and sky lights set to movable and distance fields are turned on.
The normals are all facing the right direction.
The Mesh is twosided and about 1-2 cm thick. The problem still exists on 10 cm thick meshes.
“Shadow two sided” is checked in the static mesh component settings.
The Material of the helmet is set to Two sided and is a medium rough metal.

Use unlit, or fake lit material for it.

Or use lighting channels.

Unfortunately, removing the helmet from the lighting completely is not an option, as I still need the inside of the helmet to be lit and responsive to the environment. If I move it into a different lighting channel it also stops casting a shadow on the ground, making my character appear headless to any observant player.

Have 2 actors for the inside of the helmet in the same place, have one set to a different lighting channel (in order to stay unlit from the sun), and the other actor check the options for hidden shadow and actor hidden in game.

Try to use Inset shadow for that helmet. Then it will get per object shadow map which greatly increase z precision for selfshadows.

If the helmet is only meant as an immersive effect that is placed around the camera I wouldn’t use an actual helmet model to do it. I’d make something custom with perhaps an unlit texture to fake the effect.