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Unformatted text preview: ove 4 BSP Tree. 5
5a 1. Choose polygon arbitrarily
2. Divide scene into front
(relative to normal) and back
halfspaces.
3. Split any polygon lying on
both sides.
4. Choose a polygon from each
side – split scene again.
5. Recursively divide each side
until each node contains only 1
polygon.
Lecture 9 5b 2
3 1 4 front
1
2
5a 3 back
4
5b 19/10/2007
* BSP Tree. 5
5a 1. Choose polygon arbitrarily
2. Divide scene into front
(relative to normal) and back
halfspaces.
3. Split any polygon lying on
both sides.
4. Choose a polygon from each
side – split scene again.
5. Recursively divide each side
until each node contains only 1
polygon. 5b 2 3 1 4 3 front
front
5a 2 back
4
5b 1 BSP Tree. 5
5a
5b 2 1. Choose polygon arbitrarily
2. Divide scene into front
(relative to normal) and back
halfspaces.
3. Split any polygon lying on
both sides.
4. Choose a polygon from each
side – split scene again.
5. Recursively divide each side
until each node contains only
1 polygon. 3
1 4 3 front
2 4 front
5a back 1 5b Displaying a BSP tree.
● BSP tree can be traversed to yield a correct priority list
for an arbitrary viewpoint.
•Backtofront : same as painter’s algorithm
•Fronttoback : a more efficient approach Lecture 9 19/10/2007 Displaying a BSP tree :
Back to Front .
● Start at root polygon. ○ If viewer is in front halfspace, draw polygons behind root first,
then the root polygon, then polygons in front.
○ If viewer is in back halfspace, draw polygons in front of root
first, then the root polygon, then polygons behind.
○ If polygon is on edge – either can be used.
○ Recursively descend the tree. ● If eye is in rea...
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 Spring '14

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