Many ways to go about it.
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you can toggle meshes or decal visibility on/off based on player input.
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you can use the depth buffer stencil and mask objects within a post process material.
You have to work at it, but you can fade the new PP material in and out too.
Those are probably the best options.
You should probably pick and research 2.
Unless you need special glow effects. In which case you may just need to combine 1 and 2…