cs148: introduction to computer graphics and imaging midterm review session

CS148: Introduction to Computer Graphics and Imaging

Midterm Review Session

CS148 Midterm Review Pat Hanrahan, Winter 2007

Outline

Midterm info

Review of topics

Drawing in OpenGL

Geometry: points, lines, vectors

Transforms and coordinate systems

Fonts/typography

Splines

Input devices and interaction

Color

Cameras and perspective


Midterm info

Time: Tue, Feb 13th at 7pm

Location: Building 260, Rm 113

Duration: 2 hours

Closed book

Consists of a few (4 or 5) multi-part questions

All material through last lecture (cameras)

Strongly emphasized: material on assignments

Focus on: material from lectures

Also covered: material from readings


Drawing in OpenGL

OpenGL primitives

glBegin/glEnd

Double buffering

GLUT events

display

reshape

keyboard


Geometry

Dot product

Cross product

What are orthonormal vectors?

Can you add two points?

What do you get when you add a vector to a point?


Geometry

Line defined by (x1, y1) and (x2, y2)

What is parametric form?

What is implicit form?

Which side of the line is point P on?


Transforms

Think about them in two ways

Applying to object

Applying to coordinate axes

Order matters


Transforms

Translate(1,1)

Rotate(45O)


Transforms – Apply to object

Translate(1,1)

Rotate(45O)


Transforms – Apply to coordinate system

Translate(1,1)

Rotate(45O)


Transforms – order matters

Translate(1,0)

Rotate(45O)

Rotate(45O)Translate(1,

0)


Transforms – order matters

Scale(2,2)Translate(0,

1)

Translate(0,1)

Scale(2,2)


Transforms

Homogeneous coordinates

Transforms as matrices

100

030

002

200

020

002

100

110

101

100

05.886.

0886.5.

1000

0100

1001.0

10001.


Transforms

Homogeneous coordinates

Transforms as matrices

100

030

002

200

020

002

100

110

101

100

05.886.

0886.5.

1000

0100

1001.0

10001.

glScalef(2.0, 3.0) No change glTranslatef(1.0, 1.0)

glRotatef(60.0, 0.0, 0.0, 1.0)gluOrtho (0, 200, 0, 200,-1.0, 1.0)


Transforms

Some volume of coordinate space is viewable on screen.

Orthographic projection

glOrtho/gluOrtho2D

Perspective projection

gluPerspective

glFrustum


Transforms

Transforms implemented as matrix vector multiplications

1

0

1

glTranslate

glRotate

glScale

glRotate

glScale

glRotate

glTranslate

gluPerspective

glViewport

Modeling transform(object space to world space)

Viewing transform(world space to camera space)

Projection transform(camera space to clip space)

(to window coordinates)

[vertex V]Ex: (1,0) in object space

M1 M2 M3 M4 M5 M6 M9…=

Vertex position in window= (vx,vy)

1

vy

vx


Typography

Font units

Terminology

Character map

Glyphs + glyph metrics

Kerning

Leading


Interpolation

Have discrete set of points

Want continuous function going through points


Interpolation

Bilinear interpolation

Barycentric interpolation

V3

V2V1

3

2 1V

V = 1V1 + 2V2 + 3V3

1 + 2 + 3 = 1


Interpolation

Want curve p(t) to go through all control points Ci


Cubic splines

Basis functions (Bi’s) are cubic polynomials

Different basis functions yield splines with different properties

Hermite Splines

Catmull-Rom Splines

Bezier Splines

)()()()()( 33221100 tBptBptBptBptf


Input devices

The user presses a key. What happens?


Input devices

The user presses a key. What happens?

Scan code (make and break codes)

Virtual key code

Glyph index

Glyph


Input devices

How does a mouse work?

What is quadrature encoding?

Joystick input

Axes/buttons/D-pads


Interaction

Polling vs. events

Events

Event loop

Event queues

Callbacks (event handlers)

Associating events with objects

Propagating events

Model-view-controller pattern


Physics of light

Energy from source distributed across many wavelengths: S()

Units: Watts


Physics of light

Adding light

L() = E1() + E2()

Filtering light

L() = T()E()

Sensor Response

dERR )()(


Color perception

What color do we perceive from E()?

Explain statement: humans have trichromatic color vision

Rods and Cones


Color perception

What is the CIEXYZ color space?

Why is the region within the spectral locus the span of all observable colors?

Luminance

Think: Response of rods to E()

Units = lumens

Lightness = Luminance1/3


Cameras and Lenses

Pinhole camera

film

f

x’

(x,z)

pinhole

Field of view


Cameras and Lenses

Pinhole camera

z

fxx '

film

f

x’

(x,z)

pinhole

Field of view

f

xfov ')

2tan(


Cameras and Lenses

Focal length

How does is correspond to zoom?

Depth of field

Can a pinhole camera produce depth of field effects?

Bayer mosaic

cs148: introduction to computer graphics and imaging midterm review session

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