320491 – advanced graphics · 3d laser scanner. 320491: advanced graphics - chapter 1 47...

Visualization and Computer Graphics LabJacobs University

320491 – Advanced Graphics

Prof. Dr.-Ing. Lars Linsen

Jacobs UniversitySpring 2015

320491: Advanced Graphics - Chapter 1 2


0. Introduction



0.1 Syllabus



Course Website

http://www.faculty.jacobs-university.de/llinsen/teaching/320491.htm

(accessible through CampusWeb)



Content

Computer graphics deals with the digital synthesis and manipulation of visual content, typically embedded in a three-dimensional scene. Prominent tasks in computer graphics are geometry processing, rendering, and animation. – Geometry processing is concerned with object

representations such as surfaces and their modeling,– rendering is concerned with simulating light transport to get

physically-based photorealistic images of 3D scenes or applying a certain style to create non-photorealistic images, and

– animation is concerned with descriptions for objects that move or deform over time.

Methods that tackle these three tasks are being taught.



Pre-requisites

• 320322 Graphics and Visualization

Co-requisites

• 320621 Advanced Graphics Lab(for graduate students)



Lectures

• Times: – Monday 9:45am-11am – Wednesday 8:15am–9:30am.

• Location: West Hall 5



Instructor

• Lars Linsen• Office: Res I, 128.• Phone: 3196• E-Mail: l.linsen [@jacobs-university.de]• Office hours: by appointment



Assignments

There will be three assignments:

Due: May 6Handed out: Apr 15Project 3:

Due: Apr 15Handed out: Mar 18Project 2:

Due: Mar 18Handed out: Feb 18Project 1:



Exams

There will be a midterm and a final examination. It is planned to have a written midterm and an oral final examination.



Grading

The assignments will contribute 20%, the midterm exam 30%, and the final exam 50% to the overall grade.



Dates – Lectures (1)

Lecture 1318.03.Lecture 1216.03.Week 7:No lecture – off campus11.03.Lecture 1109.03.Week 6:Lecture 1004.03.Lecture 902.03.Week 5:Lecture 825.02.Lecture 723.02.Week 4:Lecture 618.02.Lecture 516.02.Week 3:Lecture 411.02.Lecture 309.02.Week 2:Lecture 204.02.Lecture 102.02.Week 1:



Dates – Lectures (2)

Lecture 2613.05.Lecture 2511.05.Week 14:Lecture 2406.05.Lecture 2304.05.Week 13:Lecture 2229.04.Lecture 2127.04.Week 12:Lecture 2022.04.Lecture 1920.04.Week 11:Lecture 1815.04.Lecture 1713.04.Week 10:Lecture 1608.04.Holiday06.04.Week 9:

Spring breakLecture 1525.03.Lecture 1423.03.Week 8:



Dates - Exams

• Midterm: 23.03.• Final: tbd (finals week)



Lab

• There will be no exams.

• There will be 5 course-accompanying project assignments. Solutions that are handed in late lead to reduced credit (-15% per day). Exceptions are only made with an official excuse.

• The grade is to 100% based on the projects.



Dates - Assignments

Due: 13.05.Handed out: 29.04.Project 5:Due: 29.04.Handed out: 15.04.Project 4:Due: 15.04.Handed out: 18.03.Project 3:Due: 18.03.Handed out: 04.03.Project 2:Due: 04.03.Handed out: 11.02.Project 1:



Literature

• Rick Parent: Computer Animation: Algorithms and Techniques, Morgan Kaufman Publishers, 2nd Edition, 2007.

• Matt Pharr & Greg Humphreys: Physically-based Rendering: From Theory to Implementation, Elsevier, 2nd Edition, 2010.

• Selected journal and conference proceedings papers as announced in class.

• Dave Shreiner, Mason Woo, and Jackie Neider: OpenGL Programming Guide: The Official Guide to Learning OpenGL, Addison-Wesley Longman, 3rd edition, 2006. (Old version available at http://www.glprogramming.com/red.)

• Randi J. Rost and Bill Licea-Kane: OpenGL Shading Language, Addison-Wesley, 3rd edition, 2009.



0.2 Goal



Goal

Deepen and broaden concepts and techniques in 3D computer graphics.



0.3 Content



Content

Modeling

Animation

Rendering

• mesh data structures• subdivision surfaces• multiresolution meshes• mesh smoothing• mesh parametrization • deformation

• morphing• particle systems• spring-mass models• applications

• global illumination• monte carlo methods• light field• lumigraph• non-photorealism

GPU programming:• GL shading language



Examples



320322 revisited

1. Geometric Background2. Object Representation3. Raster Graphics4. Color Models5. Illumination6. Shading7. Global Illumination8. Textures9. Data Visualization10. Curves and Surfaces



Graphics Programming

• Graphical user interface (GUI)• Windowing system

– X– Integrated in OS: Microsoft Windows, Mac OS

• Microsoft Direct3D• OpenGL (Open Graphics Library)• OpenGL 2.0 (and higher)

– GLSL (GL Shading Language)• Cg (nVidia)• HLSL (high level shader language, DirectX)• GPGPU programming: CUDA (nVidia), CTM (ATI),

OpenCL



1. Modeling



Goal

Changing the shape of objects• to adjust to desired look• to improve shape• to improve representation / appearance



Driving questions

• How can we modify the shape?• What representations support these changes?• How can we obtain intuitive modeling operations?• How can we obtain interactive modeling operations?• How can we fix undesired changes quickly?• How can we improve appearance?• How can we improve quality?• How can we judge quality?



1.1 Object representation (revisited)



Boundary representations

Objects are typically represented by theirboundary surfaces.



Manifold surfaces

Boundary representations lead to manifold surfaces, i.e. 2-manifolds.Definition:• A 2-manifold is a surface, where for each surface

point the surface is locally homeomorphic to a disk.

non-manifold surface



Topology

Genus = number of handles

genus 0 genus 1 genus 2



Homeomorphism

homeomorph = topologically isomorph



Acquisition vs. generation



Implicit vs. explicit representation

explicit implicit

generated

acquired



A. Explicit surface representations



Explicit surface representations

polygonal meshes



Heightfield



Arbitrary triangular mesh



„Almost“ regular triangular mesh



„Almost“ regular quadrilateral mesh



Euler formula

For closed polygonal meshesV – E + F = 2 (1-g)

withV = # verticesE = # edgesF = # facesg = genus

Example: Cube8 – 12 + 6 = 2



3D Laser Scanner



Point Cloud



Surface Reconstruction



Point Cloud Rendering



Splat-based Rendering



Computer Aided Geometric Design



Piecewise polynomial surfaces

Freeform surfaces• Bézier surfaces• B-spline surfaces



B. Implicit surface representations



Quadrics

ellipsoid



Hyperboloid



Paraboloid



Constructive Solid Geometry (CSG)



Boolean operations



Volume data



Isosurface



C. Conversion



Implicit to explicit

Isosurface extraction• E.g. Marching Cubes



Explicit to implicit

Create a signed distance field• generate a grid• compute at each grid point the signed distance to

the surface



1.2 Mesh Data Structures



References

• Mario Botsch, Mark Pauly, Leif Kobbelt, Pierre Alliez, Bruno Lévy, Stephan Bischoff, and Christian Rössl, Geometric modeling based on polygonal meshes. SIGGRAPH '07: ACM SIGGRAPH 2007 courses, ACM, 2007.

• Kenneth I. Joy, Justin Legakis, and Ron MacCracken: Data Structures for Multiresolution Representationof Unstructured Meshes. in: HierarchicalApproximation and Geometric Methods for ScientificVisualization, Gerald Farin, Hans Hagen, and Bernd Hamann (editors), Springer-Verlag, Heidelberg, Germany, 2002.



Polygon soup

• array of vertices• array of polygons (stored as sequence of vertex indices)Example:• vertices = [(v1.x,v1.y,v1.z), …]• triangles = [(1,2,3),(2,3,4),…]Advantage: memory efficient

320491 – advanced graphics · 3d laser scanner. 320491: advanced graphics - chapter 1 47...

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