D8 cellsportals goalwalkthrougharchitectural

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Unformatted text preview: eed to test its children D7 Efficient View­Frustum Culling • What shape should bounding volumes be? – Spheres and axis­aligned bounding boxes: simple to calculate, cheap to test – Oriented bounding boxes converge asymptotically faster in theory – Lots of other volumes have been proposed, but most people still use spheres or AABBs. D8 Cells & Portals • • Goal: walk through architectural models (buildings, cities, catacombs) These divide naturally into cells – Rooms, alcoves, corridors… • Transparent portals connect cells – Doorways, entrances, windows… • Notice: cells only see other cells through portals D9 Cells & Portals • An example: D10 Cells & Portals • Idea: – Cells form the basic unit of PVS – Create an adjacency graph of cells – Starting with cell containing eyepoint, traverse graph, rendering visible cells – A cell is only visible if it can be seen through a sequence of portals • So cell visibility reduces to testing portal sequences for a line of sight… D11 Cells & Portals E A D B F C G H A B E C D H F G D12 Cells & Portals E A D B F C G H A B E C D H F G D13 Cells & Portals E A D B F C G H A B E C D H F G D14 Cells & Portals E A D B F C G H A B E C D H F G D15 Cells & Portals E A D B F C G H A B E C D H F G D16 Cells & Portals A D B C ? E F G H A B E C D F G ? H D17 Cells & Portals E A D B C X F G H A B E C D X H F G D18 Cells & Portals • View­independent solution: find all cells a particular cell could possibly see: E A D B F C G H C can only see A, D, E, and H D19 Cells & Portals • View­independent solution: find all cells a particular cell could possibly see: E A D B F C G H H will never see F D20 Cells and Portals • Questions: – How can we detect whether a given cell is visible from a given viewpoint? – How can we detect view­independent visibility between cells? • The key insight: – These problems reduce to eye­portal and portal­portal visibility D21 Cells and Portals • Airey (1990): view­independent only – Portal­portal visibility determined by ray­ casting • Non­conservative portal­portal test resulted in occasional errors in PVS – Slow preprocess – Order­of­magnitud...
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This note was uploaded on 12/09/2011 for the course CS 561/661 taught by Professor Lubke during the Summer '11 term at Virginia Tech.

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