Problems that require Visualisation. Visualisation of flow. - - PDF document

SLIDE 1

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 1

Applications Applications

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• f

3D Computer Graphics. 3D Computer Graphics.

Gordon Watson, Edinburgh Virtual Environment Centre.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 2

Computer Graphics.

• Why ? – what can we use it for ?
• How ? – does it work ?
• Where ? – is it going ?

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 3

Why ? - Applications.

• Aesthetic.

– Entertainment: games, cinema, art.

• Visuals can be either ‘realistic’ or abstract.
• Can draw inspiration from existing forms of art,

e.g cartoon, or can be totally different.

• Allows new forms of artistic expression.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 4

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 5

Applications.

• Human-Computer interaction.

– Interfaces, Computer-aided-design. – Hypertext, browsing the web. – 2D interfaces covered in future lecture. – Allow user to interact in 3D with 3D input device. – 3D displays becoming more commonplace. Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 6

Applications.

• Visualisation.

– Converting numbers into images.

• Human visual system has greatest bandwidth

– Understanding large amounts of data. – Understand abstract concepts and ideas. – Increasing need for visualisation. – The real, and unique, power of computer graphics lies in the ability to interact with, and view data in 3D.

SLIDE 2

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 7

Problems that require Visualisation.

• Medical

– Need to understand nature of 3D structures inside patient. – Data are from 3D X-ray or radiation scanners.

• Scientific

– Simulations produce huge amounts of data. – Mathematical models are frequently multi-dimensional.

• Environment.

– Need to compare observations about the Earth. – NASA Earth observation system collects over 3Tb per day.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 8

Visualisation of flow.

• Streamlines show flow

direction.

• Color shows speed.
• Gives insight into complex

interaction between vortices.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 9

‘Virtual Wind Tunnel’ at NASA Ames.

Dataset name and year # points # timesteps size (Mb) Tapered Cylinder ’90

131,000 400 1,050

McDonnell Douglas F-18 ’92

1,200,000 400 12,800

Descending delta wing ’93

900,000 1,800 64,800

Bell-Boeing V-22 tiltrotor ’93

1,300,000 1,450 140,000

Bell-Boeing V-22 tiltrotor ’96

5,000,000 1,450 300,000

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 10

Rate of information ‘uptake’

12,500

Visualisation and Pattern Recognition

60

Hearing

3-40

Reading

2

Mouse Operations.

1

Typing at 10 bytes per second

Units of Information transfer. Action

(Source : Silicon Graphics Inc.)

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 11

Video excerpts.

Artistic Expression.

• Faux Plafond. – Cosmic Promenade

– A piece inspired by geometry of world maps.

• More later if we have time…

Visualisation.

• Volume Visualisation of the Orion Nebula – SDSC.

– Visualising the 3D structure of an object seen from Earth.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 12

How does computer graphics work?

• Computer graphics are a mathematical simulation.
• What needs to be simulated ?

– Shape of 3D objects – 3D geometry. – Appearance of surfaces.

• How does the surface interact with light?
• Shininess, colour, roughness.

– Light sources. – Camera with perspective.

SLIDE 3

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 13

The shape of some 3D objects.

Paul Debevec’s Façade (1996).

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 14

Paul Debevec’s Façade (1996).

The appearance of some 3D objects.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 15

The polygon: building block of graphics.

Vertex Polygon ( frequently need to be triangles. )

So how do we do curves ??

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 16

A trip down the Graphics Pipeline... A trip down the Graphics Pipeline...

The Scene we’re trying to draw:

Images courtesy of Picture inc.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 17

Wireframe – Technical drawing style view

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 18

Perspective View from virtual camera

‘Hidden’ lines not removed

SLIDE 4

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 19

Hidden lines removed – colours added.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 20

Polygons filled with a constant colour.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 21

Simple diffuse shading model applied.

Objects have a diffuse ‘matt’ surface. Objects that should be smooth appear faceted.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 22

Smoothly curved surfaces.

Needs A LOT of polygons

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 23

Add appearance properties - shininess.

Note, lights are assumed to be ‘distant’.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 24

Texture mapping – wrapping pictures round objects.

SLIDE 5

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 25

Reflections, shadows and bumpy surfaces.

Difficult to do properly in real- time.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 26

For interaction, graphics have to be fast !

• Requirement for real-time.

– Interaction with user requires real-time response.

• Also need to model and simulate dynamics of

moving objects.

• Challenging task to do 25 times a second.

– Huge number of sums going on every second ! – Much of graphics technology is concerned with simplifying and approximations ! Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 27

Where is it going ? – some trends.

• A trend is convergence of photography and

graphics.

– Millions of flat polygons required to model complex shapes. – Can we get away with fewer if we use images to represent detail ? – Rather than try to model lighting, can we capture it from a real scene ?

• Ultimate challenge: synthetic humans.

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 28

Image-based lighting.

Image from Paul Debevec The lighting has been ‘captured’ from a real scene

Applications of Computer Graphics.

CL1h 2002. Gordon Watson http://www.edvec.ed.ac.uk 29

Summary of computer graphics.

• Graphics have many applications.

– Many aesthetic, but also useful for understanding data. – Very powerful for understanding large, complex 3D datasets.

• Graphics are a simulation.

– Need to model surface geometry and interaction with light (appearance). – Need to model dynamics and interaction.

• Graphics need to be fast.

– Need to be able to draw things in ‘real time’. – Very powerful if user can interact with the ‘simulation’.