Trigonometry and Vector Algebra: Lecture Notes for Cap4720 Fall2008 - Prof. Juraj Obert, Exams of Computer Graphics

An introduction to trigonometry and vector algebra as covered in the cap4720 fall2008 course at ucf. Topics include angles, trigonometric functions, triangle laws, points, vectors, vector algebra, and geometric primitives. Learn about the unit circle, vector magnitudes, scalar and vector products, and more.

Typology: Exams

Pre 2010

Uploaded on 11/08/2009

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Juraj Obert
http://graphics.cs.ucf.edu/cap4720/fall2008/
Trigonometry
Angles:
φ
2π−φ
Length of the arc of the unit circle
that is cut by two directions.
Which arc?
Convention: The arc swept out
counterclockwise from the first line
to the second line.
unit: Radian
conversion:
degrees*
180
radians
radians*
180
degrees
π
π
=
=
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12

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Download Trigonometry and Vector Algebra: Lecture Notes for Cap4720 Fall2008 - Prof. Juraj Obert and more Exams Computer Graphics in PDF only on Docsity!

Juraj [email protected] http://graphics.cs.ucf.edu/cap4720/fall2008/

Trigonometry

 Angles: φ 2π−φ

Length of the arc of the unit circlethat is cut by two directions. Which arc?Convention: The arc swept out counterclockwise from the first lineto the second line. unit: Radian conversion: * degrees radians 180

degrees^180 *radians =^ ππ

=

Trigonometry

 Trigonometric functions:

h

b

h

in p

cos

s

φ

φ φ^ p b

h

Trigonometry

 Triangle Laws:

trianglearea 41 ( )( )( )( )

(Lawoftangents) tan 2

tan 2

2 cos (Lawofcosines)

sin sin sin (Lawofsines) 2 2 2

a b c a b c a b c a b c

A B

A B a b

a b

c a b ab C

c

C b

B a

A

= + + − + + − + + −

^ − 

= ^ +^  −

= + −

= =

c b

a C (^) A

B

Geometric Primitives

 Polygons  circular sequence (cycle) of points (vertices) and segments (edges)

Some Geometric Problems

Segment intersection: Given two segments, do they intersect

Inclusion in polygon: Is a point inside or outside a polygon?

Simple closed path: intersecting polygon with vertices on the points. given a set of points, find a non-

Segment Intersection

 Test whether segments (a,b) and (c,d) intersect. How do we do it? a

c b

d

Point Inclusion

 given a polygon and a point  is the point inside? or  outside the polygon?

Vector

 Magnitude? Q' = (x 1 - x, y 1 - y, z 1 - z) | V | = √√√√(( x 1 -x )^2 + ( y 1 -y )^2 + ( z 1 - z )^2 )

Z^ X

Y

P

V Q Q'

Unit vector : | V |=

aV

Vector Algebra

 Scalar Multiplication : for V = (V a V = x^ , V (aVy^ , Vx , aVz)y , aVz)

V How to make a Unit Vector?

V

V '= V

Vector Algebra

 Vector addition: V 1 +^ V 2 = ( V1x +^ V2x , V1y +^ V2y , V1z +^ V2z )

V 1

V 2 V^1

+ V^2

Vector Algebra

 Scalar Product (dot product): V 1 V 2 = | = V V 1x 1 | |. V V (^2) 2x | cos + V^ 1y θθθθ. V2y + V1z. V2z

V (^2) θ V 1

Vector Algebra

 Vector product ( V cross product ): 1 ××××^ V 2 = (V1y.V2z - V1z.V2y , V1z.V2x - V1x.V2z , V1x.V2y - V1y.V2x)

x y z

x y z

V V V

V V V

i j k

2 2 2

1 1 1

Magnitude of the vector is the area of the shaded region.

Vector Algebra

 Cross product is a Vector.  Right-hand rule determines the direction of the productvector

V (^2) V 1

V^1 ××××^ V^2 θ

Basis Vectors

 A set of axis vectors is called a basis.

Z^ X

Y

Ortho-normal Basis

 normal basis : A basis with unit axis vectors.  orthogonal basis perpendicular axis vectors. : A basis with mutually  Ortho-normal basis mutually perpendicular axis vectors. : A basis with unit and  orthonormal basis for a 3D cartesian co-ordinatesystem is: i = (1,0,0), j = (0,1,0), k = (0,0,1)

Matrix

 Matrix is a rectangular array of numbers. example: a 4×3 matrix

41 42 43

31 32 33

21 22 23

11 12 13

a a a

a a a

a a a

a a a

:represents column.

:representsrowand

: theelementsofthematrix, j

i

aij

Special Matrices

 Square Matrix:

of rows = # of columns

 Row Matrix:  a single rows of elements  Column Matrix:  a single column of elements

[ 1 − 3 1 ]

Special Matrices

 Diagonal Matrix  a square matrix with all except diagonals are 0i.e. a ij = 0 if^ i^ ≠^ j.

44

33

22

11

0 0 0

a

a

a

a

Diagonal Matrix

 Identity Matrix  All diagonal elements are 1.  denoted by symbol I  example:



×^ =
I 33

Matrix Arithmatic

 Multiplication (or product) of matrices:  possible only if  # columns in 1st^ matrix = # rows in 2nd^ matrix.  i.e. if A is a m × n matrix and B is n × p matrix  then matrices are conformable for multiplicationand the product matrix C is a m × p matrix

Product of Matrices

 The elements of the product of two matrices A and B:

cij = ∑ k aikbkj

3111 32 21 3112 32 22

2111 22 21 2112 22 22

1111 12 21 1112 12 22 21 22

11 12 31 32

21 22

11 12

example :

a b a b a b a b

a b a b a b a b

a b a b a b a b b b

b b a a

a a

a a

Product of Matrices

 example:

Scalar product of vectors A and B:^ ∑

cij = (^) k aikbkj

[ ] [ ]

[ ] 112233

3

2

1 1 2 3

ab ab a b b

b

b A B AB a a a

A a a a B b b b

T (^) = + + 

Product of Matrices

example:

Vector Product of vectors A and B:^ ∑

cij = (^) k aikbkj

[ ] [ ]

[ 2 3 3 2 3 1 1 3 1 2 2 1 ]

3

2

1 2 1

3 1

3 2

1 2 3 1 2 3

ab ab ab ab ab a b

b

b

b a a

a a

a a A B

A a a a B b b b

× =