Lecture_Chapter6_b

On viewing positionorientation visibility tests tree

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Unformatted text preview: ruction A C1 B1 D3 D1 E1 B2 D2 C2 E2 G3 G2 G1 F E3 ECS 175 Chapter 6: Scene Representation and Interaction 43 BSP Tree •  BSP-Tree Applications •  Painter’s algorithm (sorting) •  Planes sort objects into (“behind” and “in front”) •  Tree traversal dependent on viewing position/orientation •  Visibility tests •  Tree computation is performed offline •  Tree computation as pre-processing •  Visibility information between nodes •  Drawbacks: •  Increases number of polygons •  Requires costly ordering and intersecting •  Assumes static geometry ECS 175 Chapter 6: Scene Representation and Interaction 44 Quadtrees and Octrees •  Quadtrees subdivide space in a predefined way parents have four child nodes axis aligned separation planes cell widths are halved ECS 175 Chapter 6: Scene Representation and Interaction 45 Quadtrees and Octrees •  Quadtree example: •  Image compression •  Octrees (in 3D) have eight child nodes per parent ECS 175 Chapter 6: Scene Representation and Interaction 46 Quadtrees and Octrees •  Quadtree example: •  Hierarchical collision test ECS 175 Chapter 6: Scene Representation and Interaction 47 Scene Representation - Summary •  Scenes consist of multiple objects in the same frame •  Hierarchical representations (trees) are important for •  Compound/Mechanical objects •  Kinematic skeleton/chain represents relative transformations •  Scene composition using a scene graph •  Hierarchical, object-oriented representation •  Object instancing, relative properties •  Can be combined with spatial partitioning technique •  Spatial partitioning/Spatial subdivision •  Pre-computed visibility tests •  Pre-computed relative ordering •  Hierarchical representation (compression) •  Hierarchical spatial operations (collision test) ECS 175 Chapter 6: Scene Representation and Interaction 48...
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This document was uploaded on 03/12/2014 for the course ECS 175 at UC Davis.

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