Landscape Visibility Question submitted by (05 January 2000) | Return to The Archives

| I'm coding currently on a landscape-engine with Direct3D and all landscape-tiles (4-point-polygons) around the player of a radius are drawn. So polygons are drawn too if they are lying behind the players view! (invisible). How could I find out which landscape-tile is visible and which's not? Do you have some sourcecode examples for me? I've tried to code some stuff with the player-vector etc. ...but I failed! |

| Often times, clipping takes care of this. During the clipping process, each vertex is "coded". This coding involves determining the binary value of a few bits that represent if a vertex is on- or off-screen in any direction. These bits are later ANDed together to quickly determine if the polygon is on- or off-screen. This explanation is certainly not good enough to learn from. But you can start with a document on 3D clipping I wrote a while ago.
Since you're doing a terrain-based engine, you can take advantage of the 2-dimensional grid that you're working with. You might want to read up on quad-trees. Quad-trees are a popular way of storing your terrain data so that you can quickly cull out large clumps of land in the time it takes to cull a single polygon. They do this by storing the data heirarchically. If a polygon node in the tree is not visible, then all of the polygons in that node can be considered not visible. Quad-trees are certainly a viable option even for beginners, yet powerful enough to yield great results.
Response provided by Paul Nettle

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