IMA Workshop on Computer Graphics

Computer GraphicsOverview

• Based on Dr. Kun Zhou’s slides• I’m responsible for all the mistakes if any.

IMA Workshop on Computer Graphics

Computer Graphics

• Visual Effects

• All about FUN– Films, games

More seriously

• CAGD• Scientific Visualization• Information Visualization• Medical Imaging• Simulation & Training• Virtual Reality• Image/Video Processing

IMA Workshop on Computer Graphics

Where to Play?• Conferences (incomplete list)

– General: ACM SIGGRAPH, EUROGRAPHICS, Pacific Graphics, i3D

– Animation: SCA, CASA

– Modeling: SGP, SoCG, SMI, SPM, SMA

– Rendering: EGSR, NPAR

– Others: GDC, IEEE-VR, CGIM, VIS, InfoVis

• Journals (incomplete list)– ACM ToG, IEEE TVCG, CGF, VC, C&G, etc

The Graphics Process

3D Geometric Models

3D Animation Definition

Lighting Information

Rendering

Texture Information

Image Storage and

Display

IMA Workshop on Computer Graphics

Geometric Modeling

• How do we …– Represent 3D objects

– Construct 3D objects

– Manipulate 3D objects

Geometric Modeling

• How do we …– Represent 3D objects

– Construct 3D objects

– Manipulate 3D objects

IMA Workshop on Computer Graphics

Represent 3D Objects• Triangular Mesh

Represent 3D Objects• Triangular Mesh

IMA Workshop on Computer Graphics

Represent 3D Objects

• Subdivision Surface– coarse mesh & subdivision rule

Represent 3D Objects• Subdivision Surface

IMA Workshop on Computer Graphics

Represent 3D Objects

• Parametric Surface• z = f (x, y),more generally x=f(u,v), y=g(u,v), z=h(u,v)

Represent 3D Objects• Implicit Surface

• f (x, y, z) = 0

IMA Workshop on Computer Graphics

Geometric Modeling

• How do we …– Represent 3D objects

– Construct 3D objects

– Manipulate 3D objects

Construct 3D Objects

• 3D Scanning

CyberwareMetris

IMA Workshop on Computer Graphics

Construct 3D Objects

• 3D Scanning

[Digital Michelangelo Project]

Construct 3D Objects• Interactive Modeling

– the world in basic shapes

IMA Workshop on Computer Graphics

Construct 3D Objects

• Interactive Modeling– the world in basic shapes

Example: Suggestive Sketch• [Tsang 04 (image below), Igarashi01]

IMA Workshop on Computer Graphics

Construct 3D Objects

• Interactive Modeling– Maya, 3DS Max, ZBrush

Construct 3D Objects• Displacement Map

IMA Workshop on Computer Graphics

Construct 3D Objects• Displacement Map

Geometric Modeling

• How do we …– Represent 3D objects

– Construct 3D objects

– Manipulate 3D objects

IMA Workshop on Computer Graphics

Manipulate 3D Objects

• 3D Mesh Deformation

GPU implementation

IMA Workshop on Computer Graphics

Texturing• What’s texture?

Texturing• What’s texture?

IMA Workshop on Computer Graphics

Texturing• What’s texture?

Texturing

• Make 3D objects realistic

without texture with texture

IMA Workshop on Computer Graphics

Texturing

• Texture Painting– Laborious, require artistic skills

[Igarashi and Cosgrove 2001] [Lévy 2003]

Texturing

• Texture Synthesis– Automatic, only repeated patterns

[Praun et al. 2000] [Zhang et al. 2003]

IMA Workshop on Computer Graphics

Texturing

• Texture Mapping– Interactive, easy to use

Stanford Bunny6 photographs of another bunny

Texturing

• Texture Montage

IMA Workshop on Computer Graphics

Texture Mapping Triangle MeshVertex 1 xVertex 1 x11 yy11 zz11Vertex 2 xVertex 2 x22 yy22 zz22……

Face 2 Face 2 11 33Face 4 2 3Face 4 2 3……

Texture Mapping Triangle MeshVertex 1 xVertex 1 x11 yy11 zz11Vertex 2 xVertex 2 x22 yy22 zz22……

ss11 tt11ss22 tt22

ss

tt

Face 2 Face 2 11 33Face 4 2 3Face 4 2 3……

IMA Workshop on Computer Graphics

Texture Mapping Triangle MeshVertex 1 xVertex 1 x11 yy11 zz11Vertex 2 xVertex 2 x22 yy22 zz22……

ss11 tt11ss22 tt22

Face 2 Face 2 11 33Face 4 2 3Face 4 2 3……

ss

tt

Rendering

• Turning everything into pictures

RenderingImage

Storage & Display

3D Geometric Models

3D Animation Definition

Transformation, Clipping,

Perspective

Image Generation

Texture Information

IMA Workshop on Computer Graphics

Rendering

• Interaction of Light and Matter

light

eye

Rendering Equation

light

eye

iioiiio dnVLB ωωωωρωωωrrrrrrrr

),0max(),()()()( ⋅= ∫

nr

oωr

iωr

IMA Workshop on Computer Graphics

Rendering: BRDFs

Rendering: Shadows

without shadow with shadow

IMA Workshop on Computer Graphics

Rendering: Inter-reflections

without inter-reflection with inter-reflection

Rendering: Caustics

without caustics with caustics

IMA Workshop on Computer Graphics

Rendering: Translucent

BRDF BSSRDF

Real-time Rendering

TransportTransportComplexityComplexity

LightingLighting

simplesimple shadowsshadows

pointpointlightslights

full full envenv..mapmap

interinter--reflectionsreflections

singlesingleareaarealightlight

[Moeller02][Moeller02]

[Blinn76][Blinn76]

[Heidrich00][Heidrich00]

[Crow77][Crow77]

[Ashikhmin02][Ashikhmin02]

PrecomputedPrecomputedRadiance Radiance TransferTransfer

[Sloan02][Ng03][Zhou05][Ren06][Sun07]

IMA Workshop on Computer Graphics

Precomputed Radiance Transfer

( )V sr

( ) ( )i iL s l B s=∑r r%

( )( ) ( ) ( ) ( , ) ( )i i NR v l B s V s f s v H s d s= ∑∫r r r r r r r%

( ) ( ) ( ) ( , ) ( )i i NR v l B s V s f s v H s d s=∑ ∫r r r r r r r%

( ) max( ,0)NH s s N= •Preprocess for all Preprocess for all ii

vr

( ) ( ) ( ) ( , ) ( )NR v L s V s f s v H s d s= ∫r r r r r r r

( ) i iR v l t=∑r%

Precomputed Radiance Transfer

Basis 16Basis 16

Basis 17Basis 17

Basis 18Basis 18

illuminateilluminate resultresult

......

......

IMA Workshop on Computer Graphics

Other rendering methods

• Rasterization• Raytracing

– Distributed raytracing– Path tracing

• Radiosity• Reyes

Implicit Visibility

[Dachsbacher 07]

IMA Workshop on Computer Graphics

Character Animation

• Mostly commonly modeled by rigging• Motion specified by

– Keyframing (often w/ IK)– Mocap (retargeted)

Data-driven Example

IMA Workshop on Computer Graphics

Simulation

• Physics-based (inspired)– Finite Element Method– Variational Principle

• Various Speed-up techniques (hacks)– Precomputation– Low-res sim. combined w/ captured details– Model reduction

Simulation Example