visible surface detection

Visible Surface Detection CEng 477 Introduction to Computer Graphics Fall 2006

Visible Surface Detection ,[object Object],[object Object],[object Object],[object Object],[object Object]

Object Space Methods ,[object Object],[object Object],[object Object],[object Object],[object Object]

Image Space Methods ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Depth Cueing ,[object Object],[object Object]

Back-Face Detection ,[object Object],[object Object],[object Object],[object Object]

Back-Face Detection ,[object Object],[object Object]

Back-Face Detection ,[object Object]

Depth-Buffer Method ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Depth-Buffer Method ,[object Object],[object Object],[object Object],[object Object]

Depth-Buffer Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Calculating depth values efficiently ,[object Object],[object Object]

Calculating depth values efficiently ,[object Object]

Depth-Buffer Method ,[object Object],View from the Right-side

Z-Buffer and Transparency ,[object Object],[object Object],[object Object],Partially transparent Opaque Opaque 1st 2nd 3rd Front 1st or 2nd 1st or 2nd Must recall this color and depth OK. No Problem Problematic Ordering 3rd: Need depth of 1st and 2nd

A-Buffer Method ,[object Object],[object Object],[object Object]

Ray Casting Algorithm ,[object Object],[object Object],Viewer View Plane A B C D E It is like a variation of the depth-buffer algorithm, in which we proceed pixel by pixel instead of proceeding surface by surface.

Depth Sorting ,[object Object],6 6 5 2 3 4 1 1 1 2 1 2 3 1 2 3 4 1 2 3 4 5 1 2 3 4 5

Depth-sort algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Depth-sort algorithm ,[object Object],depth max depth min

Depth-sort algorithm ,[object Object],z x surface 1 surface 2

Depth-sort algorithm ,[object Object],[object Object]

Depth-sort algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Depth-sort algorithm P Q if they do, test fails x - extents not overlap? z x

Depth-sort algorithm if they do, test fails y - extents not overlap? P Q z y

Depth-sort algorithm Is P entirely behind the surface Q relative to the viewing position (i.e., behind Q’s plane with respect to the viewport)? z x P Q Test is true…

Depth-sort algorithm Is Q entirely in front of P's plane relative to the viewing position (i.e., the viewport)? z x P Q Test is true…

Depth-sort algorithm Do the projections of P and Q onto the (x,y) plane not overlap? z x P Q y x P Q hole in P Test is true…

Depth-sort algorithm ,[object Object],[object Object],[object Object],[object Object]

Binary Space Partitioning ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Building BSP-Trees ,[object Object],[object Object],[object Object],[object Object]

BSP-Tree Example A C B 2 4 1 3 A B C 3 2 4 1 - - - + + +

Using a BSP-Tree ,[object Object],[object Object],[object Object],[object Object],Spliting plane

Rendering BSP Trees ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

BSP-Tree: Advantages ,[object Object]

[object Object],[object Object],[object Object],[object Object],BSP-Tree: Disadvantages Ouch

visible surface detection

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visible surface detection