This illustration shows a top-down view of a 3D scene, where each blue edge corr
ID: 3675137 • Letter: T
Question
This illustration shows a top-down view of a 3D scene, where each blue edge corresponds to a planar square perpendicular to the image plane (i.e. coming out of the page) and the eye of an alternative viewpoint lies in the image plane. The short vectors are normal vectors. The eye locations are illustrated by the black dots e_1 and e_2. Draw a BSP tree for the above scene by adding the segments in the labeled order (i.e. from 'a' to 'h', breaking segments as necessary). Describe how your tree will be traversed when rendering the scene from the eye location e_1. Then describe how it would be traversed from e_2.Explanation / Answer
inary space partitioning was developed in the context of 3D computer graphics,[1][2] where the structure of a BSP tree allows spatial information about the objects in a scene that is useful in rendering, such as their ordering from front-to-back with respect to a viewer at a given location, to be accessed rapidly. Other applications include performing geometrical operations with shapes (constructive solid geometry) in CAD,[3] collision detection in robotics and 3-D video games, ray tracing and other computer applications that involve handling of complex spatial scenes.
Choose a polygon P from the list. Make a node N in the BSP tree, and add P to the list of polygons at that node. For each other polygon in the list: If that polygon is wholly in front of the plane containing P, move that polygon to the list of nodes in front of P.
We choose a line, A, from the image
Add to it a a node
We split the remaining lines in the list into those in front of A (i.e. B, C,),and
(g,f), and (D,E)
We first process the lines in front of A (in steps ii–v),..
Followed by those behind (in steps vi–vii)
A BSP tree is traversed in a linear time, in an order determined by the particular function of the tree. Again using the example of rendering double-sided polygons using the painter's algorithm, to draw a polygon P correctly requires that all polygons behind the plane P lies in must be drawn first, then polygon P, then finally the polygons in front of P. If this drawing order is satisfied for all polygons in a scene, then the entire scene renders in the correct order. This procedure can be implemented by recursively traversing a BSP tree .
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