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OpenGL Introduction
and HW1 Guide
Speaker: Yu Tu CSIE
M2
This guide is talking about…
1.Part of computer graphics
2.OpenGL introduction
3.Sample codes discussion :
line.cpp, robot.c, dance.c
Part of computer graphics
Computer Graphics Pipeline
Model in Graphics
- object observation
Model in Graphics
- coordinate system
World
coordinate
Image
coordinate
Camera
coordinate
OpenGL Introduction
What is OpenGL
•
A Graphics rendering API introduced in 1992
by Silicon Graphics Inc
•
Produces high-quality color images composed
of geometric and image primitives
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Cross-platform
Related APIs
Application program
GLUT
AGL,WGL,GLX
X Window, Windows, Mac OSX
GLU
GL
Software and/or hardware
OpenGL Utility Toolkit (GLUT)
•
Visual Studio 2010/2008, Visual C++ 2010/2008
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http://www.xmission.com/~nate/glut.html
•
Add glut32.dll to
•
Add glut32.lib to
•
Add glut.h to
C:\Windows\SysWOW64
(System32)
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\lib
(9.0)
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\GL
(9.0)
HelloWorld
#include <GL/glut.h>
void GL_display();
void GL_reshape(GLsizei w, GLsizei h);
void main(void)
{
glutCreateWindow(“HelloWorld");
glutDisplayFunc(GL_display);
glutReshapeFunc(GL_reshape);
glutMainLoop();
}
HelloWorld
void GL_display()
{
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin( GL_LINES );
glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f(1.0f, 1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(-1.0, 1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f);
glEnd();
glFlush();
}
Primitives
HelloWorld
void GL_display()
{
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin( GL_LINES );
glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f(1.0f, 1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(-1.0, 1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f);
glEnd();
glFlush();
}
HelloWorld
void GL_reshape(GLsizei w, GLsizei h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-2.0f, 2.0f, -2.0f, 2.0f, -2.0f, 2.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
Now that you have done your first OpenGL Program,
let’s talk about something advanced.
Matrix in OpenGL
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There are two matrix stacks.
•
ModelView matrix (GL_MODELVIEW)
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Projection matrix (GL_PROJECTION)
When we call functions of transformation, we should
change to the appropriate matrix stack first.
•
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glMatrixMode(GL_MODELVIEW);
• //now we are in modelview matrix stack!
• //do modelview transformation here…..
glMatrixMode(GL_PROJECTION);
• //now we are in projection matrix stack!
• //do projection transformation here….
Vertex
ModelView
Projection
Projection Matrix
• Orthographic Projection
glOrtho( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top,
GLdouble near, GLdouble far )
gluOrtho2D( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top)
Projection Matrix
Perspective Projection
gluPerspective( GLdouble fovy, GLdouble aspect, GLdouble near, GLdouble
far );
glFrustum( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top,
GLdouble near, GLdouble far );
ModelView Matrix
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Modeling Transformation
•
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Perform rotate, translate, scale and combinations
of these transformations to the object.
Viewing Transformation
•
To positioning and aiming the camera
Modeling Transformations
glTranslatef(x, y, z)
Multiplies current matrix by a matrix that
moves an object by x,y,z
glTranslatef( 0, 0, -1)
Modeling Transformations
glRotatef(angle, x, y, z )
Multiplies current matrix by a matrix that
rotates an object in a counterclockwise direction
about the ray from origin to (x,y,z) with angle as
the degrees
glRotatef( 45.0, 0, 0, 1)
Modeling Transformations
glScalef (x, y, z)
Multiplies current matrix by a matrix that scales an
object along axes.
glScalef( 2.0, -0.5, 1)
Viewing Transformations
gluLookAt (eyex, eyey, eyez, atx, aty, atz,
upx, upy, upz );
Matrix Order
Code:
glMatrixMode(GL_
PROJECTION)
gluPerspective
glMatrixMode(GL_
MODELVIEW)
gluLookAt
glRotatef
glTranslatef
glScalef
glBegin
glVertex3f
glEnd
Matrix Stack:
Matrix Multiplication
glVertex3f
glScalef
gluPerspective
gluLookAt
glRotatef
glTranslatef
glRotatef
gluLookAt
gluPerspective
glTranslatef
glScalef
glVertex3f
=
Vi
Matrix Order
The order of transformations is critical.
glRotatef(45.0, 0,0,1 );
glTranslatef( 1,0,0 );
drawObject();
glTranslatef( 1,0,0 );
glRotatef(45.0, 0,0,1 );
drawObject();
Interactive Setting and Display
Glut Window functions:
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(800, 600);
glutInitWindowPosition(100, 100);
glutCreateWindow(“Name");
glutDisplayFunc(display);
glutReshapeFunc(reshape);
Interactive setting functions:
glutKeyboardFunc(keyboard);
glutMouseFunc(mouse);
glutMotionFunc(motion);
Wake up for
The most important topic.
Mantain matrix stack
•
glPushMatrix() : save the current matrix
•
glPopMatrix()
: restore the saved matrix
x
glScalef
glPushMatirx()
glPopMatrix()
Heirarchy Modeling
Body
head
Left
hand
Finger 1
Right
hand
Finger 2
Left
leg
Righ
t leg
Heirarchy Modeling
Matrix Stack:
Current Matrix
Stack
Heirarchy Modeling
Push
Matrix Stack:
Current Matrix
Stack
glPushMatrix();
Heirarchy Modeling
Push
glTranslatef();
Matrix Stack:
x
Current Matrix
Stack
Heirarchy Modeling
Push
Matrix Stack:
Current Matrix
Stack
DrawBody();
Heirarchy Modeling
Push
Matrix Stack:
Current Matrix
Stack
glPushMatrix();
Push
Heirarchy Modeling
Push
Matrix Stack:
glRotatef();
Push
x
Current Matrix
Stack
Heirarchy Modeling
Push
Matrix Stack:
glTranslatef();
Push
x
Current Matrix
Stack
Heirarchy Modeling
Push
Matrix Stack:
Current Matrix
Stack
DrawHead();
Push
Heirarchy Modeling
Push
Matrix Stack:
glPopMatrix();
Push
Pop
Current Matrix
Current Matrix
Stack
Heirarchy Modeling
Push
Matrix Stack:
glPushMatrix();
Push
Pop
Current Matrix
Stack
Push
Heirarchy Modeling
Push
Matrix Stack:
glRotatef();
Push
Pop
x
Current Matrix
Stack
Push
Heirarchy Modeling
Push
Matrix Stack:
DrawHand();
Push
Pop
Current Matrix
Stack
Push
Heirarchy Modeling
Push
Matrix Stack:
glPushMatrix();
Push
Pop
Current Matrix
Stack
Push
Push
Heirarchy Modeling
Push
Matrix Stack:
glTranslatef();
Push
Pop
Current Matrix
Stack
x
Push
Push
Heirarchy Modeling
Push
Matrix Stack:
DrawFinger();
Push
Pop
Current Matrix
Stack
Push
Push
Heirarchy Modeling
Push
Matrix Stack:
glPopMatrix();
Push
Pop
Push
Push
Pop
Current Matrix
Current Matrix
Stack
Heirarchy Modeling
Push
Body
Pop
Push
Push
Push
Left
hand
head
Pop
Right
hand
Pop
Pop
Push
Push
Finger 1
Finger 2
Pop
Pop
Push
Push
Pop
Pop
Left
leg
Righ
t leg
Contratulations !
You are well prepared for
our homework now!
Time for Sample Codes
Robot.c
glPushMatrix();
glTranslatef (-1.0, 0.0, 0.0);
glRotatef ((GLfloat) shoulder, 0.0, 0.0, 1.0);
glTranslatef (1.0, 0.0, 0.0);
glPushMatrix();
glScalef (2.0, 0.4, 1.0);
glutWireCube (1.0);
glPopMatrix();
glPushMatrix();
glTranslatef (1.0, 0.0, 0.0);
glRotatef ((GLfloat) elbow, 0.0, 0.0, 1.0);
glTranslatef (1.0, 0.0, 0.0);
glPushMatrix();
glScalef (2.0, 0.4, 1.0);
glutWireCube (1.0);
glPopMatrix();
glPopMatrix();
glPopMatrix();
Dance.c
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BOOL Open_CD(void)
BOOL Stop_CD(void)
BOOL Close_CD(void)
BOOL Play_CD(int bTrack)
int GetUnit(FILE* input)
void GetMovie(void)
void PutIntoFile(FILE* input,
int item)
void SetNull(FILE* input)
void SetRecord()
void ZoomChange()
void ColorChange(int mode)
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void init(void)
void reshape (int w, int h)
void baseroom(void)
void ManSet()
void WomanSet()
void display(void)
void keyboard (unsigned char
key, int x, int y)
int OnTimer(int value)
int main(int argc, char** argv)
Dance.c
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BOOL Open_CD(void)
Class Music{
BOOL Stop_CD(void)
…
BOOL Close_CD(void)
.
BOOL};
Play_CD(int bTrack)
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int GetUnit(FILE* input)
void GetMovie(void)
Class Script{
void PutIntoFile(FILE* input,
…
int item)
};
.input)
void SetNull(FILE*
void SetRecord()
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Class
Animation{
void
ZoomChange()
void ColorChange(int
…
}; mode)
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void ManSet()
Class Component{ … };
void WomanSet()
Class Actor{
…
};
void init(void)
void reshape (int w, int h)
void baseroom(void)
void display(void)
void keyboard (unsigned char
key, int x, int y)
int OnTimer(int value)
int main(int argc, char** argv)
Q&A