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Creating A Fog of War around a character

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    Creating A Fog of War around a character

    Here is a question that I have that if possible could create better graphics and overall playability.

    I got this idea from playing the Old Warcraft game. In the game there is an area around your character that is fogged out until you explore the area.

    Basically the same idea could be applied to a character moving through an environment. Put yourself in front of the computer and fire up UDK. Generate a character and let it run towards you changing the various angles that you are looking at it.

    In the Fog of War mode the only portion of the character model that would be rendered would be the portion of the model that you can actually see.

    This means that if you are looking at the character from the rear as in the image below.


    Wait wrong image.....basically you would see the character in front of you only. The portion of the character than you do not see, a belt or holstered gun in a belt would not be rendered until you were actually looking at that area.

    Another example could be that the same character is running away from you would see the back, legs, head and back pack of the character but if you position another camera in front of the camera you would only see a blacked out image until the position of your characters viewing area moved around to in front of the character being viewed.

    The basic princile behind what you're describing is called Occlusion Culling ( ) and has been around for ages. UE3 makes heavy use of this via precomputed visibilty ( ).

    If UE3 doesn't do what you're describing, that is remove nonvisible faces from the rendering process in realtime, my guess is that checking whether or not a player can see a face for every face of a mesh (via raytracing etc.) requires more processing power than to just render the entire mesh.


      I can indeed imagine it being extremely expensive to work out which polygons are and are not visible. It's one thing to check if bounds are visible (four points to check), but a heavily triangulaed mesh like a UT3 player model would be thousands of times more expensive.