opengl programming part ii -...

Graphics

Graphics Lab @ Korea University http://kucg.korea.ac.kr

OpenGL Programming

Part II

Korea Univ.

Computer Graphics Lab.

KUCG

Graphics Lab @ Korea University

View Volume

void glOrtho(GLdouble left, GLdouble right,

GLdouble bottom, GLdouble top, GLdouble zNear,

GLdouble zFar)

void glFrustum(GLdouble left, GLdouble right,

GLdouble bottom, GLdouble top, GLdouble zNear,

GLdouble zFar)

void gluPerspective(GLdouble fov,

GLdouble aspect, GLdouble near, GLdouble far)

fov : field of view (degree, 0~180)

aspect : aspect ratio (Width/Height)

near : near clipping plane

far : far clipping plane

http://kucg.korea.ac.kr

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How the View Volume Works (1/2)

glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);

glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);

Projection

Projection


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How the View Volume Works (2/2)

glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);

glOrtho(-3.0, 3.0, -3.0, 3.0, -1.0, 1.0);

Projection

Projection


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glFrustum Example


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Viewing Parameters

View Reference Point (px, py, pz)

Eye point

View Direction (dx, dy, dz)

Up Vector (ux, uy, uz)

Field of view (xfov, yfov)

Viewplane

“Look at” point

Viewplane normal

Up Vector

Right

Vector

View Reference

Point

Viewplane

“Look at” Point

View Direction


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Viewing Transformation

void gluLookAt(GLdouble eyex, GLdouble eyey, GLdouble eyez,

GLdouble atx, GLdouble aty, GLdouble atz, GLdouble upx, GLdouble upy,

GLdouble upz)

eyex, eyey, eyez : Camera Position(x, y, z)

atx, aty, atz : Camera Focus(x, y, z)

upx, upy, upz : Camera Up-vector

Default

gluLookAt(0.0, 0.0, 0.0, 0.0, 0.0, -100.0, 0.0, 1.0, 0.0);


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gluLookAt Example


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Viewport Transformation

glViewport(GLint x, GLint y, GLsizei width, GLsizei height)

Left-low corner coordinate (x, y)

Viewport size (width, height)

Example // initialize the size of a window

glutInitWindowSize(200, 200);

// sets the position and size of a viewport

glViewport(0, 0, 100, 100); (0, 0) (100, 0) (200, 0)

(0, 100)

(0, 200)


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Viewport Example


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Callback Functions (1/3)

void glutReshapeFunc(void(*func)(int width,

int height))

Registers the callback function called when the

window size or shape is changed

width : new width of a window

height : new height of a window

void glutKeyboardFunc(void(*func)(unsigned char key, int x,

int y))

Registers the callback function called when a key is

pressed

key : ASCII code of the pressed key

(x, y) : the coordinate of a mouse


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Keyboard Callback Example


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void glutMouseFunc(void(*func)(int button, int state, int x, int y))

Registers the callback function called when a mouse button is pressed button

GLUT_LEFT_BUTTON , GLUT_RIGHT_BUTTON, GLUT_MIDDLE_BUTTON

state

GLUT_DOWN, GLUT_UP

(x, y) : the coordinate of a mouse

void glutMotionFunc(void(*func)(int x, int y))

Registers the callback function called when a mouse is dragged

void glutPassiveMotionFunc(void(*func)(int x, int y))

Registers the callback function called when a mouse is moved without being pressed


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Mouse Callback Example


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void glutIdleFunc(void (*func)(void))

Registers the callback function called when there are

no events to be processed idle time


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Front Face Detection (1/2)

GLuint glFrontFace(GLenum mode)

Determine which direction of the face definition is the

front face

mode

GL_CCW : counter-clockwise (default)

GL_CW : clockwise

GLuint glCullFace(GLenum mode)

Determine which face must be culled

mode

GL_FRONT

GL_BACK (default)


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Front Face Detection (2/2)

void glEnable/glDisable(GLenum feature)

Enable or disable the operation of OpenGL according

to the macro „feature‟

feature

GL_CULL_FACE

Default : glDisable(GL_CULL_FACE);


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Matrix-related Functions (1/2)

void glMatrixMode(GLenum mode)

Sets the type of a matrix stack to be processed

mode

GL_MODELVIEW

When we move the object

GL_PROJECTION

When we define the clipping view volume

GL_TEXTURE

When we manipulate the texture coordinates

void glLoadIdentity()

Loads the identity matrix on the current matrix stack


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Matrix-related Functions (2/2)

void glLoadMatrixf(const GLfloat *M)

Loads the given matrix on the current matrix stack

void glMultMatrixf(const GLfloat *M)

Multiplies the given matrix with the current matrix of

the matrix stack

*M

16-length array

means 4x4 matrix

Column-major notation

151173

141062

13951

12840

mmmm

mmmm

mmmm

mmmm


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Transformations : Rotation

void glRotatef(GLfloat angle, GLfloat x, GLfloat y, GLfloat z)

Rotation axis (x, y, z)

Example // Declare the transformation mode

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

// z-Rotate the objects by 45 degree

glRotatef(45.0, 0.0, 0.0, 1.0);

// Draw the solid cube

glutSolidCube(0.3);


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Transformations : Translation

void glTranslatef(GLfloat dx, GLfloat dy, GLfloat dz)

Example glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

// Translate the objects by (0.5, -0.5, 0.0)

glTranslatef(0.5, -0.5, 0.0);

glutSolidCube(0.3);


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Transformations : Scaling

void glScalef(GLfloat sx, GLfloat sy, GLfloat sz)

Example glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

// Scale the objects by (2.0, 1.0, 1.0)

glScalef(2.0, 1.0, 1.0);

glutSolidCube(0.3);


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Composite Transformation Example


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OpenGL Lighting

Turn on the „lighting calculation‟ and each „light

source‟ glEnable(GL_LIGHTING);

glEnable(GL_LIGHT0);

All colors will be assigned based on

Light sources and

Material properties

Not by glColor3f( )

Maximum # of Light Sources : 8(GL_LIGHT0~7)


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Enable Lighting (1/2)


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Enable Lighting (2/2)


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Light Function

void glLightfv(GLenum light, GLenum pname, const GLfloat*

params)

Selects one of the available light sources and assigns its

various properties

Light

GL_LIGHT0 ~ GL_LIGHT7

pname

Parameter name

params

Parameter value

ex)

float ambientLight[] = {1.0f, 1.0f, 1.0f, 1.0f}; // white ambient light

glLightfv(GL_LIGHT0, GL_AMBIENT, ambientLight); // sets ambient light property


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Light Function Parameters

pname Default Value Meaning

GL_POSITION (0.0, 0.0, 1.0, 0.0) Light Position (x, y, z, w)

GL_SPOT_DIRECTION (0.0, 0.0, -1.0) Spotlight Direction Vector (x, y, z)

GL_SPOT_CUTOFF 180.0 Spotlight Cutoff Angle

GL_SPOT_EXPONENT 0.0 Spotlight Concentrating Factor n

GL_AMBIENT (0.0, 0.0, 0.0, 1.0) Ambient Light Intensity

GL_DIFFUSE (1.0, 1.0, 1.0, 1.0) Diffuse Light Intensity

GL_SPECULAR (1.0, 1.0, 1.0, 1.0) Specular Light Intensity

GL_CONSTANT_ATTENUNATION 1.0 Attenuation Constant Coefficient k0

GL_LINEAR_ATTENUATION 0.0 Attenuation Linear Coefficient k1

GL_QUADRATIC_ATTENUNATION 0.0 Attenuation Quadratic Coefficient k2

2

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1

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Light Position

GL_POSITION

(x, y, z, 1) : point light source at (x, y, z)

(x, y, z, 0) : directional light source from (x, y, z) direction

ex)

GLfloat LightPosition[] = {0.0, 1.0, 0.0, 0.0};

glLightfv(GL_LIGHT0, GL_POSITION, LightPosition);

GLfloat LightPosition[] = {-1.0, 1.0, 0.0, 0.0};

glLightfv(GL_LIGHT0, GL_POSITION, LightPosition);


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Spotlight

Set a point light source

Then assign some spotlight properties

GL_SPOT_CUTOFF

GL_SPOT_DIRECTION

GL_SPOT_EXPONENT


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Material Property

void glMaterialfv(GLenum face, GLenum pname, GLfloat *param)

Defines material properties for the light calculation

face : where to apply

GL_FRONT, GL_BACK, GL_FRONT_AND_BACK

pname : property name

param : property value

pname Meaning

GL_AMBIENT Ambient Coefficient Ka

GL_DIFFUSE Diffuse Coefficient Kd

GL_AMBIENT_AND_DIFFUSE Ambient/Diffuse Coefficient Ka & Kd

GL_SPECULAR Specular Coefficient Ks

GL_SHININESS Reflection Concentrating Factor n

GL_EMISSION Emitted Light Intensity


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Lighting Models

void glLightModelfv(GLenum pname, GLfloat* param)

pname : property name

param : property value

Pname Meaning

GL_LIGHT_MODEL_AMBIENT Ambient Light Intensity

Default : (0.2, 0.2, 0.2, 1.0)

GL_LIGHT_MODEL_LOCAL_VIWER Set the viewing vector same to the all polygons or not?

Default : GL_FALSE (Same)

GL_LIGHT_MODEL_TWO_SIDE Illuminate the back faces or not?

Default : GL_FALSE (Only Front Faces)


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Specifying a Light Source

Defaults for “glEnable(GL_LIGHT0)”

No ambient light

Diffuse and specular component

(1.0, 1.0, 1.0, 1.0) pure white

Position

(0.0, 0.0, 1.0, 0.0) directional light

void glLightfv(GLenum light, GLenum param, TYPE *value)

light

GL_LIGHT0, GL_LIGHT1, …

param

GL_POSITION, GL_DIFFUSE, GL_SPECLAR, GL_AMBIENT


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light for glLightfv()

Directional Light

GL_POSITION, GL_DIFFUSE, GL_SPECULAR,

GL_AMBIENT

Point Light

GL_CONSTANT_ATTENUATION,

GL_LINEAR_ATTENUATION,

GL_QUADRATIC_ATTENUATION

Spotlight

GL_SPOT_DIRECTION, GL_SPOT_CUTOFF,

GL_SPOT_EXPONENT

2

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Lighting Example


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Point Light (1/2)


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Point Light (2/2)


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Control of Light Position (1/4)


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Complex Light (1/2)


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Complex Light (2/2)


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Attenuation : Point Light (1/2)


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Attenuation : Point Light (2/2)


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Spotlight (1/4)


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Spotlight (2/4)


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Spotlight (3/4)


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Spotlight (4/4)


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Multiple Lights (1/2)


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Multiple Lights (2/2)


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Specifying a Material (1/5)

void glMaterialfv(GLenum face, GLenum name, TYPE*

value)

Defines the material reflection properties

face

GL_FRONT, GL_BACK, GL_FRONT_AND_BACK

name

GL_DIFFUSE, GL_SPECLAR, GL_AMBIENT,

GL_AMBIENT_AND_DIFFUSE, GL_EMISSION,

GL_SHININESS


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White Shiny Material (1/2)


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White Shiny Material (2/2)


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Brass Material (1/2)


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Brass Material (2/2)


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Red Plastic Material (1/2)


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Red Plastic Material (2/2)


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Multiple Objects (1/2)


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Multiple Objects (2/2)


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