# Visible - Visible-Surface Detection Methods Chapter 9 Intro...

This preview shows pages 1–8. Sign up to view the full content.

Visible-Surface Detection Methods Chapter 9 Intro. to Computer Graphics Spring 2009, Y. G. Shin

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
The Visibility Problem [Problem Statement] GIVEN: a set of 3-D surfaces, a projection from 3-D to 2-D screen, DETERMINE: the nearest surface encountered at any point on 2-D screen Remove of hidden parts of an object Hidden-surface removal : surface rendering Hidden-line removal : line drawing
Techniques Visible-surface algorithms are 3D versions of sorting, i.e., depth comparison Avoid comparing all pairs of objects using the following coherence: object coherence: no comparison between components of objects if objects are separated each other face coherence: surface properties vary smoothly across a face edge coherence: an edge changes its visibility not frequently

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Techniques implied edge coherence: line of intersection of two face can be determined from two intersection points scan-line coherence: little change in visible spans from one scanline to another area coherence: a group of pixels is often covered by the same visible surface span coherence: (special case of area coherence) homogeneous runs in a scanline depth coherence: adjacent parts of the same surface are typically close in depth frame coherence: animation frames contain small changes from the previous frame
Techniques for Efficient Algorithms Bounding volumes approximate complex objects with simple enclosures before making comparisons. the simplest approximate enclosure is a boundary box

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Backface Removal (Backface Culling) Remove entire polygons that face away from the viewer If we are dealing with a single convex object, culling completely solves the hidden surface problem Geometric test for the visibility surface visible : 0 < N V V N s silhouette : 0 = N V
Back-face Culling More..

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern