Cohen sutherland algorithm how to extend to 3d also

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Unformatted text preview: • Select a clip edge based on the outcode, split and feed the new segment on the side of the rectangle back into algorithm • Need to perform 4 intersection checks for each line. Cohen-Sutherland algorithm • How to extend to 3D? – Also clipping the lines using front / back planes • How many bits needed for the outcode? Cohen-Sutherland algorithm • How to extend to 3D? – Also clipping the lines using front / back planes • How many bits needed for the outcode? Polygon Clipping: Sutherland-Hodgman’s algorithm • A systematic approach to clip polygons • Input : A 2D polygon • Output : a list of vertices of the clipped polygon Polygons are clipped at each edge of the window while traversing the polygon Sutherland-Hodgman’s algorithm • The edges of the polygon are traversed • The edges can be divided into four types Inside Outside Output Vertex Inside Outside Output Intersection Case 1 Case 2. Inside Outside Case 3 No output. Inside Outside First Output Second Output Case 4 Sutherland-Hodgman’s algorithm For each edge of the clipping rectangle For each edge of the polygon (connecting pi, pi+1) • If case 1 add p+1 to the output • If case 2 add interaction to output • If case 4 add intersection and p+1 to output Inside Outside Output Vertex Case 1 Inside Outside Output Intersection Case 2. Inside Outside Case 3 No output. Inside Outside Second Output First Output Case 4 Example Sutherland-Hodgman algorithm • How to extend to 3D? Summary Projection Perspective, parallel (orthographic) projection Canonical view volume Clipping Cohen-Sutherland’s algorithm Sutherland-Hodgmans’s algorithm Another Good Modern Textbook http://www.realtimerendering.com/ Akenine-Moller Readings • Foley et al. Chapter 6 – all of it, • Particularly section 6.5 • Introductory text, Chapter 6 – all of it, • Particularly section 6.6 • Akenine-Moller, Real-time Rendering Chapter 3.5 • Clipping lines, polygons • Foley et al. Chapter 3.12, 3.14 • http://www.cc.gatech.edu/grads/h/Hao-wei. Hsieh/Haowei.Hsieh/mm.html...
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