C OpenGL Tutorial

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C/OpenGL Tutorial
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OUTLINE

• C Tutorial
• CG Vocabulary
• OpenGL Tutorial

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C Tutorial
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Rule of thumb

• You dont have to try out everything just because
  with C everything is possible

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OUTLINE C Tutorial

• Syntax differences on the low-level
• Constants
• Classes
• Pointers
• Memory management
• In/Output
• Using vectors and co.
• What is unique for Java?
• Useful links

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Syntax differences on the low-level ( 1 )

• The unsigned keyword
• unsigned int ranges in 0, max int
• Analogy for byte, short, long etc.
• Not boolean but bool
• This is valid
• a b 1
• Equivalent if statements
• if( number ! 0 )
• if( number )

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Syntax differences on the low-level ( 2 )

• Beware
• if( a b )
• instead
• Compiles unlike Java
• Arrays declaration
• int vertices 10
• Size fixed in declaration
• We can trick it anyway ?

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Syntax differences on the low-level ( 3 )

• Beware
• There are no IndexOutOfBoundsExceptions
• You have to check it yourself
• Or use stdvector or similar
• Prevents You from
• Accessing (read/write) not allocated memory
• Reading data from any location
• Undesired application crash

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Constants and macros

• Defining a constant
• define MAX_SIZE 10
• Usually without semicolon!
• define MAX_SIZE 10
• means MAX_SIZE is 10
• After text replacement

mysize factor MAX_SIZE asize
mysize factor 10 asize
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Classes ( 1 )

• A class structure (in a header file ex. pair.h)
• An example class

• class Pair
• public
• Pair ( ) // The default constructor
• Pair ( int x, int y ) // The constructor
• Pair ( ) // The destructor
• int getX ( )
• int getY ( )
• void setX ( int newValue )
• void setY ( int newValue )
• private
• int x
• int y

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Classes ( 2 )

• Function declaration in the .h (header) file
• Function definition in the .cpp file
• include pair.h
• Example function definition

void PairsetX( int _x ) x _x
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Classes ( 3 )

• Q How to avoid cyclic includes?
• A Compiler directives.
• Ex. define, ifdef, ifndef, else, elseif,
  endif
• Example code

ifndef _PAIR_H define _PAIR_H_ class Pair
endif
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Classes inheritance

• Dynamical binding not by default in C
• virtual keyword necessary (example)

class Secretary Employee //Secretary extends
Employee public Secretary( int id ) virtual
void work( ) private void write( ) int
identity

• SecretarySecretary( int id ) Employee( id ),
  identity( id )
• void Secretarywork( )
• Employeework( )
• write( )

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Pointers ( 1 )

• Variable containing an address to another
  variable
• 310 char achar array
• 410 double pi 3.14
• 411 long flag 0
• 412 char pchar achar
• 510 char pstr string
• 610 long pli flag

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Pointers ( 2 )

• Example
• Prints
• i 42 intptr 42

int intptr int i 13, j 29 intptr i
// address operator intptr j //
dereference operator stdcout ltlt i ltlt
i stdcout ltlt intptr ltlt intptr ltlt stdendl
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Pointers ( 3 )

• Dereferencing objects example
• Special operator -gt
• b-gtdie( ) is equivalent to ( b ).die( )
• b is the value, the bambus and die( ) its
  member

• BambusTree b new BambusTree( )
• BambusTree btree
• b-gtgrow( 20.0f ) // dereferencing
• b-gtdie( )
• btree.grow( 20.0f )
• btree.die( )

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Pointers ( 4 )

• Call by value
• Parameter passing of a function
• Call by reference
• Passing an address as a parameter
• Changes the functions arguments outside the
  function
• Example

//function add add(int a, int b, int sum)sum
ab int summand1 2, summand2 3 int
result add( summand1, summand2, result )
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Memory management ( 1 )

• After creating a new object, we have ALLOCATED
  memory which WE must FREE
• All pointers set with new must be set free
• For each new we must provide a delete
• Example (static destructor for simple objects)

BambusTree b new BambusTree( ) delete b
//calls a destructor of the class BambusTree b
null
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Memory management ( 2 )

• Arrays are also pointers, freeing memory
  necessary too
• Example (dynamic destructor for arrays)
• Use memory leak checkers

int riceField riceField new int 12
delete riceField riceField null
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In/Output ( 1 )

• Reading from a file
• We include ltiostreamgt, ltfstreamgt, ltstringgt
• Setup declare/define the necessary
• Reading itself

stdstring filename name // name is a
parameter stdifstream in_str( filename.c_str(),
stdifstreamin ) stdstring currentLine
stdgetline( ( in_str ), currentLine ) // the
whole line is as a string in currentLine
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In/Output ( 2 )

• Reading from a file ( 2 )
• String handling examples
• Erasing
• currentLine.erase( 0, 3 )
• Getting ints and floats
• int index float u float v
• sscanf_s( currentLine.c_str( ), "d f f,
  index, u, v )
• // currentLine expected to be ex. 1 0.567 0.789
• Accessing a single character

currentLine.erase( 0, 3 )
int index float u float v sscanf_s(currentLine.
c_str(),"d f f,index,u,v) // currentLine
expected to be ex. 1 0.567 0.789
switch( currentLine 0 ) case '' case
'?'
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In/Output ( 3 )

• Reading from a file ( 3 )
• Closing the input stream
• in_str.close( )
• Useful print a float/int variable to a buffer
• char buffer 64
• float radius 5
• float perimeter 31.4159f
• sprintf_s( buffer, "d f", radius, perimeter )
  // 5 31.4159
• Writing to a command line

in_str.close( )
char buffer 64 float radius 5 float
perimeter 31.4159f sprintf_s( buffer, "d
f", radius, perimeter ) // 5 31.4159
stdcout ltlt radius ltlt ltlt perimeter ltlt
stdendl stdcerr ltlt ERROR OCCURED ltlt
stdendl stdcin.get() // wait until key
pressed, then close exit( 1 )
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Using stdvector ( 1 )

• C brother of Java-vector class
• Grows dynamically
• definition
• stdvectorlt Bambus gt bv
• An empty vector of elements type Bambus
• stdvectorlt Bambus gt bv( 100 )
• A Bambus-vector with 100 elements
• Default constructor necessary

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Using stdvector ( 2 )

• bv a vectorlt Bambus gt, b Bambus
• clear( ) resize(100) push_back( b) pop_back(
  )
• Accessing elements
• Many other useful functions

for( int i 0 i lt bv.size() i ) //bv i

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Features unique for java

• Thread handling is easy
• synchronized keyword
• instanceof operator
• Interfaces
• Java is interpreted!

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Useful links

• Online reference
• http//www.cplusplus.com/
• MS Development Network
• www.msdn.com
• Moving from java to C
• http//www.horstmann.com/ccj2/ccjapp3.html
• http//www-ali.cs.umass.edu/mckinley/377/labs/c
  _for_java_programmers.html
• C Kurs
• http//www.mathematik.uni-marburg.de/cpp/

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OpenGL Tutorial
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CG Vocabulary

• Fixed function pipeline
• Programmable pipeline
• LightNing vs. Lighting
• Gouraud shading
• QuaterNion vs. Quaterion

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OpenGL Tutorial - Outline

• How to get OpenGL
• Setup project
• Concepts (state machine, stacks)
• Viewing pipeline
• Textures
• Lighting
• Render with immediate mode
• Create window, context with Glut
• Input handling with Glut

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How to get OpenGL

• API standard maintained by Khronos group
• Implemented by graphics card vendors
• Current OpenGL version v2.1
• Windows includes only v1.1
• Get somewhere else (Cg Toolkit 1)
• Resources at 2

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Setup project

• Include files
• Link libraries
• opengl32.lib
• glu32.lib

include ltGL/gl.hgt //basic OpenGL include
ltGL/glu.hgt //OpenGL utility functions
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Concepts 1/2 - State machine

• OpenGL command syntax
• Certain amount of states are present
• states set to certain mode, active until change
• On/Off states (eg. backface culling)
• Variable states (eg. current color)
• Call to get value of states

glCommand1234sifd(Type x1, Type x2,
...) GL_CONSTANT //syntax for OpenGL constants
glGet() //several calls beginning with get
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Concepts 2/2 - Stacks

• Stacks for different sets of variables
• Attribute stack
• All states can be saved

glPushAttrib() //saves the current attribs on
stack glPopAttrib() //restores last saved attribs

• Matrix stack
• GL_PROJECTION
• GL_MODELVIEW
• GL_TEXTURE

glMatrixMode(GL_MODE) //sets the matrix
mode glPushMatrix() //saves the matrix on
stack glPopMatrix() //restores the last saved
matrix
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Viewing pipeline 1/4

• Modifications of matrices
• Translation
• Scale
• Rotation
• Calls always multiply the current active matrix

glTranslatefd(TYPE x, TYPE y, TYPE z)
glScalefd(TYPE x, TYPE y, TYPE z)
glRotatefd(TYPE angle, TYPE x, TYPE y, TYPE z)
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Viewing pipeline 2/4

• Perspective projection via GL_PROJECTION matrix
  mode
• Build projection out of camera parameters
• Important!
• Clear the matrix before changing

glFrustum(l, r, b, t, n, f) //perspective
projection glOrtho(l, r, b, t, n,
f) //orthographic projection
gluPerspective(fov, aspect, near, far)
glLoadIdentity()
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Viewing pipeline 3/4

• Model and view matrix via GL_MODELVIEW
• Must be rebuilt when camera position changes

gluLookAt(eyex, eyey, eyez, centerx, centery,
centerz, upx, upy, upz)
//camera changes glLoadIdentity() gluLookAt( ...
) //creates view matrix //render Models foreach
object glPushMatrix() //store on Matrix
stack transform and render model //modelview
created glPopMatrix() //recover view matrix
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Viewing pipeline 4/4

• Advanced methods
• Generate one yourself
• Multiply by current matrix

glMatrixMode(GL_MODE) float myMatrix new
float16 //generate the matrix you
want glLoadMatrixf(myMatrix) //replaces current
matrix //with given
glMatrixMode(GL_MODE) float myMatrix new
float16 //generate the matrix you
want glMultMatrixf(myMatrix) //multiplies
current matrix //with given
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Textures 1/4

• Texture activation
• Have to be enabled
• Unique handle for each texture
• Bind active texture
• Must be done every frame for every texture that
  is needed

glEnable(GL_TEXTURE_2D)
int myHandle glGenTextures(1, myHandle) //gener
ates handle for 1
glBindTexture(GL_TEXTURE_2D, myHandle)
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Textures 2/4

• Texture initialisation
• Load texture data into GPU memory
• Alternative build all mipmaps

enable and activate current texture int mipLevel
0 int border 0 int internalFormat
GL_RGBA, int width 800 int height 600 int
format GL_RGBA int type GL_UNSIGNED_BYTE cha
r data new charwidth height 4 //fill
data with values glTexImage(GL_TEXTURE_2D,
mipLevel, internalFormat, width, height, border,
format, type, data)
gluBuild2DMipmaps(GL_TEXTURE_2D, internalFormat,
width, height, border, format, type, data)
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Textures 3/4

• Texture environments
• State call
• Filtering types (pname)
• Filtering method (param)

glTexParameteri(GL_TEXTURE_2D, pname, param)
GL_TEXTURE_MIN_FILTER //minification
filter GL_TEXTURE_MAG_FILTER //maxification
filter
GL_NEAREST //nearest neighbour GL_LINEAR //li
near GL_NEAREST_MIPMAP_NEAREST //nn with
mipmaps GL_LINEAR_MIPMAP_LINEAR //linear with
mipmaps
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Textures 4/4

• Texture environments
• Repetition type (pname)
• Repetition method (param)

GL_TEXTURE_WRAP_S //in s direction GL_TEXTURE_WRA
P_T //in t direction
GL_CLAMP_TO_EDGE GL_REPEAT
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Lighting 1/2

• Lighting activation
• Set shading
• GL_FLAT
• GL_SMOOTH
• Enable Lighting
• Enable Light
• 8 lights supported

glShadeModel(GL_MODE)
glEnable(GL_LIGHTING)
glEnable(GL_LIGHT0)
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Lighting 2/2

• Lighting setup
• State call
• Light characteristic (pname)
• Characteristic value (param)
• Usually float4

glLightfv(GL_LIGHTi, pname, param)
GL_AMBIENT //params needed for diffuse
lighting GL_DIFFUSE //more are available GL_SPECUL
AR GL_POSITION
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Render with immediate mode

• Transfer each single vertex into GPU memory
• Different primitives
• Render primitive(s)

glTexCoord2f(u, v) //optional texcoord for
vertex glNormal3f(nx, ny, nz)//optional normal
for vertex glVertex3f(x, y, z)
GL_POINTS GL_LINES, GL_LINE_STRIP,
GL_LINE_LOOP GL_TRIANGLES, GL_TRIANGLE_STRIP,
GL_TRIANGLE_FAN GL_QUADS, GL_QUAD_STRIP,
GL_POLYGON
glBegin(GL_PRIMITIVE) calls for
vertices glEnd()
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Create window, context with Glut 1/4

• Glut OpenGL Utility Toolkit 3 4
• Platform independent window and input handling
• Link Library
• glut32.lib

include ltGL/glut.hgt //must be first gl related
include do other opengl includes
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Create window, context with Glut 2/4

• Init Glut
• Create window
• windowed
• full screen
• Game mode string
• pxwidth x pxheight depth _at_ refresh rate

glutInit(argc, argv) glutInitDisplayMode(GLUT_RG
BAGLUT_DOUBLEGLUT_DEPTH)
glutInitWindowPosition(50, 50) glutInitWindowSize
(width, height) glutCreateWindow(Windowtitle)
glutGameModeString(1024x76832_at_60) glutEnterGam
eMode()
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Create window, context with Glut 3/4

• Init OpenGL

glViewPort(0, 0, pxwidth, pxheight) glEnable(GL_
DEPTH_TEST) glDepthFunc(GL_LEQUAL) glClearDepth(
1.0f) glEnable(GL_CULL_FACE) glClearColor(0.0f
, 0.0f, 0.0f, 0.0f) //some other things done
here too, //but only in advanced OpenGL //see the
first repetitorium
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Create window, context with Glut 4/4

• Callbacks have to be set to user defined
  functions
• Rendering and idle

void myRenderScene() glClear(GL_COLOR_BUFFER_BIT
GL_DEPTH_BUFFER_BIT) update an render
scene glutSwapBuffers() int main(int argc,
char argv) init glut init opengl other glut
callbacks glutDisplayFunc(myRenderScene) //set
callback glutIdleFunc(myRenderScene) //set
callback glutMainLoop() //starts the mainloop
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Input handling with Glut 1/2

• Set callbacks
• Key down / up

float moveway 0.0f void myKeyboardFunc(int
key, int x, int y) if (key a) moveway
1.0f void myKeyboardUpFunc(int key, int x, int
y) if (key a) moveway
0.0f glutIgnoreKeyRepeat(1) //ignore
keyrepeat glutKeyboardFunc(myKeyboardFunc) glutKe
yboardUpFunc(myKeyboardUpFunc)
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Input handling with Glut 2/2

• Set callback
• Mouse move / click

void myMouseMoveFunc(int x, int y) process
mousecoordinates void myMouseFunc(int button,
int state, int x, int y) process
buttons glutPassiveMotionFunc(myMouseMoveFunc)
glutMouseFunc(myMouseFunc)
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References

• 1 nVidia Cg Toolkit http//developer.nvidia.com/
  object/cg_toolkit.html
• 2 OpenGLhttp//www.opengl.org
• 3 Gluthttp//www.xmission.com/nate/glut.html
• 4 Lighthouse3Dhttp//www.lighthouse3d.com/openg
  l/glut/