lab manual final computer graphics

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CSC 3224: Computer Graphics Lab Manual

Fall 013-14American International University

Bangladesh (AIUB)

[COMPUTER GRAPHICS:

LAB MANUAL] This Lab Manual has been developed for the undergraduate students of Computer Science department for the

fulfillment of the course CSC3224: Computer Graphics and partial fulfillment for the graduation. This manual

will be followed in the lab classes as primary reference material. Other supporting documents beside this

manual can be consulted for the better understanding of the topics.

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CSC3224: Computer Graphics Lab Manual

Table of contents

Lab Assignment 1: Introduction to OpenGL Programming.................................................... 3

Lab Assignment 2: Basic Transformation .............................................................................. 6

Lab Assignment 3: Keyboard and Mouse Interaction ............................................................ 8

Lab Assignment 4: Composite Transformation.................................................................... 13

Lab Assignment 5: Line Drawing Algorithm ....................................................................... 15

Lab Assignment 6: Circle Drawing Algorithm .................................................................... 17

Lab Assignment 7: Ellipse Drawing Algorithm ................................................................... 19

Lab Assignment 8: Polygon Filling Algorithms................................................................... 21

Lab Assignment 9: Line Clipping Algorithms ..................................................................... 23

Lab Assignment 10: Polygon Clipping Algorithms.............................................................. 25

Lab Assignment 11: Curve Generation ................................................................................ 27

Lab Assignment 12: Lighting in OpenGL............................................................................ 30

Lab Assignment 13: Color in OpenGL ................................................................................ 33

Lab Assignment 14: Animation ........................................................................................... 35

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Lab Assignment 1: Introduction to OpenGL Programming

Objective:

1. Becoming familiar with OpenGL programming structure using OpenGL Utility Toolkit (GLUT).

2. Learning how to initialize windows and objects inside a graphics window

Reference:

1. OpenGL Programming Guide, Red Book, Chapter-1

Prerequisite:

Knowledge of:

C/C++ Programming

Basic Coordinate Geometry

Academic Honesty:

All work that you do toward fulfillment of this course's expectations must be your own unless collaboration is

explicitly allowed (e.g., by some problem set or the final project). Viewing or copying another individual's work

(even if left by a printer, stored in an executable directory, or accidentally shared in the course's virtual

classroom) or lifting material from a book, magazine, website, or other sourceeven in partand presenting it

as your own constitutes academic dishonesty, as does showing or giving your work, even in part, to another

student.

Similarly is dual submission academic dishonesty: you may not submit the same or similar work to this course

that you have submitted or will submit to another. Nor may you provide or make available your or other

students' solutions to individuals who take or may take this course in the future.

You are welcome to discuss the course's material with others in order to better understand it. You may even

discuss problem sets with classmates, but you may not share code. You may also turn to the Web for instruction

beyond the course's lectures and sections, for references, and for solutions to technical difficulties, but not for

outright solutions to problems on projects. However, failure to cite (as with comments) the origin of any code or

technique that you do discover outside of the course's lectures and sections (even while respecting these

constraints) and then integrate into your own work may be considered academic dishonesty.

All forms of academic dishonesty are dealt with harshly.

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Problem Description:

Draw some basic shapes like Triangle, Polygon and fill them with various colors. The display window should be

titled with the name of the assignment.

Example Code: Drawing a Rectangle

void display(void)

{

/* clear all pixels */

glClear(GL_COLOR_BUFFER_BIT);

/* draw white polygon (rectangle) with corners at

* (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0)

*/

glColor3f(1.0, 1.0, 1.0);

glBegin(GL_POLYGON);

glVertex3f(0.25, 0.25, 0.0);

glVertex3f(0.75, 0.25, 0.0);

glVertex3f(0.75, 0.75, 0.0);

glVertex3f(0.25, 0.75, 0.0);

glEnd();

/* dont wait!

* start processing buffered OpenGL routines

*/

glFlush();

}

void init(void)

{

/* select clearing (background) color */

glClearColor(0.0, 0.0, 0.0, 0.0);

/* initialize viewing values */

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

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

}

/*

* Declare initial window size, position, and display mode

* (single buffer and RGBA). Open window with hello

* in its title bar. Call initialization routines.

* Register callback function to display graphics.

* Enter main loop and process events.

*/

Post Lab Assignment:

1. Draw all the shapes in the same window.

2. Make the window size 1024*768 px.

3. Set the window position at upper left corner of the monitor.

4. Draw an 8X8 chess board using loop.

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Evaluation Policy:

Your code will be evaluated along the following axes.

Correctness. To what extent is your code consistent with our specifications and free of bugs?

Design. To what extent is your code written well (i.e., clearly, efficiently, elegantly, and/or logically)?

Style. To what extent is your code readable (commented and indented with variables aptly named)?

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Lab Assignment 2: Basic Transformation

Objective:

To implement set of Basic Transformations on Polygon i.e. Translation, Rotation and Scaling

Reference:

1. Xiang and Plastock , Schaum's Outline Computer Graphics, Second Edition

Prerequisite:

Knowledge of:

Basic Transformation

o Translation

o Rotation

o Scaling


C/C++ Programming

Academic Honesty:






student.











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Scaling Transformations:

A 2D point can be scaled by multiplication of the coordinate values (x,y) by scaling factors Sx and Sy to

produce the transformed coordinates (x',y').

Translation Transformations:

A 2D point can be translated by adding the coordinate values (x,y) by Translation distances Tx and Ty to

produce the transformed coordinates (x',y').

Rotation Transformations:

A 2D point can be rotated by repositioning it along a circular path in the xy plane. We specify the rotation angle

and the position of the rotation point about which the object is to be rotated. Multiplication of the coordinate

values (x,y) by rotation matrix produce the transformed coordinates (x',y').

Now you have to design a program which will provide you with the option that which type of transformation

you want to do. Like the following,

Enter your choice:

1. Translation

2. Rotation

3. Scaling

4. Exit

After providing the choice you have to enter the number of edges of a polygon and then you have to input the

coordinates of each vertex. Like the following,

Enter the no. of edges:-4

Enter the co-ordinates of vertex 1:- 30 30




Enter the Translation factor for x and y:-20 20

After that you have to draw two polygons, one is the original polygon with supplied vertices and another is the

transformed one.

Evaluation Policy:





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Lab Assignment 3: Keyboard and Mouse Interaction

Objective:

1. To study and implement Mouse and Keyboard interaction with OpenGL programs.

2. To study events in OpenGL, How to handle them and use them inside an OpenGL Program.

Reference:

1. OpenGL Programming Guide, Red Book, Chapter-1

Prerequisite:

Knowledge of:

C/C++ Programming


Academic Honesty:






student.











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Draw some basic shapes like Triangle, Polygon and fill them with various colors. The display window should be

titled as the name of the assignment. Then use the provided code to spin the shape and also zoom in and zoom

out effect on the shape.

Example Code: Showing How to use Keyboard and Mouse events inside a program

This Code describes spinning and zooming for a particular object drawn inside the display function.

static GLfloat spin = 0.0;

static GLfloat spin_speed = 1.0;

float spin_x = 0;

float spin_y = 1;

float spin_z = 0;

float translate_x = 0.0;

float translate_y = 0.0;

float translate_z = -30.0;

// assuming work-window width=50unit, height=25unit;

void init()

{

glClearColor(0,0,0,0);

glShadeModel(GL_SMOOTH); // Enable Smooth Shading

glClearDepth(1.0f);

// Depth Buffer Setup

glEnable(GL_DEPTH_TEST); // Enables Depth Testing

}

//------- custom functions starts -------

void setSpin(float x, float y, float z)

{

spin_x = x;

spin_y = y;

spin_z = z;

}

void reset()

{

spin_x = 0;

spin_y = 1;

spin_z = 0;

translate_x = 0.0;

translate_y = 0.0;

translate_z = -30.0;

}

//------- custom functions ends -------

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void reshape(int w,int h)

{

glViewport(0,0, (GLsizei)w,(GLsizei)h);


glLoadIdentity();

gluPerspective(100.0f, (GLfloat)w/(GLfloat)h, 1.0f, 100.0f);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

}

void myDisplay()

{

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glLoadIdentity();

glTranslatef(translate_x, translate_y, translate_z);

glRotatef(spin,spin_x,spin_y,spin_z);

//******************************************//

//------- custom code starts -------

//------- custom code ends -------

//******************************************//

glutSwapBuffers();

}

void spinDisplay(void)

{

spin=spin+spin_speed;

if(spin>360.0)

{

spin=spin-360.0;

}

glutPostRedisplay();

}

void spinDisplayReverse(void)

{

spin=spin-spin_speed;

if(spin

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break;

if(state==GLUT_DOWN)

glutIdleFunc(spinDisplay);

case GLUT_MIDDLE_BUTTON:


{

glutIdleFunc(NULL);

}

break;

case GLUT_RIGHT_BUTTON:


glutIdleFunc(spinDisplayReverse);

break;

default:

break;

}

}

void keyboard(unsigned char key, int x, int y)

{

//-------- spin --------

if(key=='x')

{

setSpin(1.0,0.0,0.0);


}

else if(key=='y')

{

setSpin(0.0,1.0,0.0);


}

else if(key=='z')

{

setSpin(0.0,0.0,1.0);


}

else if(key=='a')

{

setSpin(1.0,1.0,1.0);


}

//-------- spin --------

//-------- zoom --------

else if(key=='i')

{

translate_z++;


}

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else if(key=='o')

{

translate_z--;


}

//-------- zoom --------

//-------- reset -------

else if(key=='r')

{

reset();


}

//-------- reset -------

}


1. Draw all the shapes in the same window.

2. Make the window size 1024*768 px.

3. Set the window position at upper left corner of the monitor.

4. Check whether all the shapes in the same window can be spinned or zoomed separately or not. If not

then state why it is not possible, If yes then submit the code within the next lab.

Evaluation Policy:





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Lab Assignment 4: Composite Transformation

Objective:

To study and Implement set of Composite Transformations on Polygon i.e. Reflection, Shear (x &y), and

Rotation about an arbitrary point.

Reference:


Prerequisite:

Knowledge of:

Composite Transformation on Polygon

o Reflection

o Shear

o Rotation about an arbitrary point


C/C++ Programming

Academic Honesty:






student.











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Rotation about an arbitrary point:

This is done by three transformation steps: translation of the arbitrary point (Xc,Yc) to the origin, rotate about

the origin, and then translate the center of rotation back to where it belongs.

To transform a point, we would multiply all the transformation matrices together to form an overall

transformation matrix.

Now you have to design a program which will provide you with the option that which type of transformation

you want to do. Like the following,

Enter your choice:

1. Reflection

2. Shearing

3. Rotation about an arbitrary point

4. Exit

After providing the choice you have to enter the number of edges of a polygon and then you have to input the

coordinates of each vertex. Like the following,

Enter the no. of edges:-4





Enter the Translation factor for x and y:-20 20

a. Reflection along X-axis

b. Reflection along Y-axis

c. Exit

Enter your choice:

After that you have to draw two polygons, one is the original polygon with supplied vertices and another is the

transformed one.

Evaluation Policy:





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Lab Assignment 5: Line Drawing Algorithm

Objective:

1. To study and implement DDA Algorithm

2. To study and implement Bresenhams Algorithm

Reference:


Prerequisite:

Knowledge of:

Point plotting Methods

DDA Algorithm

Bresenhams Algorithm

Academic Honesty:






student.











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You have to design a program which will provide you with the option that which type of Algorithm you want to

use for drawing a line. Like the following,

Enter your choice:

1. DDA Algorithm

2. Bresenham

3. Exit

After providing the choice you have to enter the coordinates of start point and end point. Like the following,

Enter a Initial Point: - 100 200

Enter the Final Point: - 200 300

After that you have to draw the line with the supplied coordinates.

Algorithm: DDA

Input to the function is two endpoints (x1,y1) and (x2,y2)

1. length abs(x2-x1);

2. if (abs(y2-y1) > length) then length abs(y2-y1);

3. xincrement (x2-x1) / length;

4. yincrement (y2-y1) / length;

5. x x + 0.5; y Y + 0.5;

6. for i 1 to length follow steps 7 to 9

7. plot (trunc(x),trunc(y));

8. x x + xincrement ;

9. y y + yincrement ;

10. stop.


1. Implement Bresenhams Algorithm for drawing a line.

2. Modify the Bresenhams Algorithm so that it will produce a dashed-line.

Evaluation Policy:





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Lab Assignment 6: Circle Drawing Algorithm

Objective:

To study and Implement Midpoint circle algorithm given the points of the centre and the radius.

Reference:


Prerequisite:

Knowledge of:

Midpoint circle Algorithm

Academic Honesty:






student.











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You have to design a program which will take input the coordinates of the center of the circle as well as the

radius. Like following,

Enter the coordinates of the centre:

X-coordinate = 350

Y-coordinate = 250

Enter the radius: 50

After that you have to draw the circle with the supplied coordinates and radius.

Algorithm: Midpoint circle algorithm

1. Input radius r and circle center (x0,y0), and obtain the first point on the circumference of a circle centered on

the origin as(x0,y0)= (0 , r)

2. Calculate the initial value of the decision parameter asp0 = 5 / 4 r

3. At each Xk position , starting at k=0, perform the following test: If pk < 0 , the next point along the circle

centered on (0,0) is (Xk + 1 ,Yk ) and pk+1 = pk + 2 Xk +1 + 1 Otherwise ,the next point along the circle is (Xk +

1, Yk -1) and pk+1 = pk + 2 Xk +1 + 1 2Yk+1 Where 2 Xk +1 = 2xk + 2 and

2Yk+1 = 2 yk-2.

4. Determine symmetry points in the other seven octants

5. Move each calculated pixel position (x,y) onto the circular path centered on (x0,y0) and plot the coordinate

values: x = x + xc, y = y + yc

6. Repeat step 3 through 5 until x>= y

Evaluation Policy:





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Lab Assignment 7: Ellipse Drawing Algorithm

Objective:

To study and Implement Midpoint Ellipse algorithm.

Reference:


Prerequisite:

Knowledge of:

Midpoint Ellipse Algorithm

Academic Honesty:






student.











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You have to design a program which will take input the coordinates of the center of the ellipse as well as the

major and minor axis. Like following,

Enter the coordinates of the centre:

X-coordinate = 350

Y-coordinate = 250

Enter the Minor axis: 50

Enter the Major axis: 100

After that you have to draw the ellipse with the supplied parameters.

Algorithm: Midpoint ellipse algorithm

1. Get parameters a, b, h, k for center coordinate h and k and major & minor axis lengths 2a and 2b.

2. Calculate the initial decision parameter value in the first region:

3. Use the formulas above to iterate pxk+1 until b2x>a

2y.

4. Rename the current (xk,yk) as (x0,y0) and calculate the initial decision parameter value in the 2nd

region:

5. Use the formulas above to iterate pyk+1 until y

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Lab Assignment 8: Polygon Filling Algorithms

Objective:

To study and Implement Polygon Filling algorithm.

Reference:


Prerequisite:

Knowledge of:

Boundary Filling Algorithm (4 and 8 connected)

Academic Honesty:






student.











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You have to design a program which will take input the coordinates of the interior points and then you have to

use the following algorithm to fill up those points.

Algorithm: Boundary Fill algorithm

(x,y) are the interior points, boundary is the boundary color and fill_color is the color to be filled. Following is a

recursive method for boundary fill.

1. present_color = getcolor() // a function which returns the current color of (x,y)

2. if present_color boundary and if present_color fill_color then repeat steps 3-7

3. set_pixel (x,y, fill_color)

4. call the algorithm recursively for points (x + 1, y)

5. call the algorithm recursively for points (x 1,y)

6. call the algorithm recursively for points (x,y + 1)

7. call the algorithm recursively for points (x,y - 1)

8. stop

Evaluation Policy:





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Lab Assignment 9: Line Clipping Algorithms

Objective:

To study and Implement Line Clipping with Cohen- Sutherland algorithm

Reference:


Prerequisite:

Knowledge of:

Cohen-Sutherland algorithm

Academic Honesty:






student.











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You have to design a program which will take input the coordinates of two end points of a line and two window

coordinates. Then you have to draw the line and clipped window. Like,

Enter Minimum window co-ordinates:- 200 250

Enter Maximum window co-ordinates:- 300 350

Enter co-ordinates of first point of line: - 180 250

Enter co-ordinates of second point of line: - 200 300

Algorithm: Cohen-Sutherland algorithm

The Cohen-Sutherland algorithm uses a divide-and-conquer strategy. The line segment's endpoints are tested to

see if the line can be trivially accepted or rejected. If the line cannot be trivially accepted or rejected, an

intersection of the line with a window edge is determined and the trivial reject/accept test is repeated. This

process is continued until the line is accepted.

To perform the trivial acceptance and rejection tests, we extend the edges of the window to divide the plane of

the window into the nine regions. Each end point of the line segment is then assigned the code of the region in

which it lies.

1. Given a line segment with endpoint P1=(X1,Y1) and P2=(X2,Y2)

2. Compute the 4-bit codes for each endpoint.

If both codes are 0000,(bitwise OR of the codes yields 0000 ) line lies completely inside the window:

pass the endpoints to the draw function.

If both codes have a 1 in the same bit position (bitwise AND of the codes is not 0000), the line lies

outside the window. It can be trivially rejected.

3. If a line cannot be trivially accepted or rejected, at least one of the two endpoints must lie outside the

window and the line segment crosses a window edge. This line must be clipped at the window edge

before being passed to the drawing routine.

4. Examine one of the endpoints, say P1=(X1,Y1). Read P1's 4-bit code in order: Left-to-Right, Bottom-to-

Top.

5. When a set bit (1) is found, compute the intersection I of the corresponding window edge with the line

from P1 to P2. Replace P1 with I and repeat the algorithm.


1. Implement the Liang-Barsky Algorithm in the same manner for clipping a line.

Evaluation Policy:





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Lab Assignment 10: Polygon Clipping Algorithms

Objective:

To study and Implement Polygon Clipping Algorithm using Sutherland - Hodgeman Algorithm

Reference:


Prerequisite:

Knowledge of:

Sutherland Hodgeman Algorithm

Academic Honesty:






student.











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You have to design a program which will take input the coordinates of two end points of a line and two window

coordinates. Then you have to draw the line and clipped window. Like,

Enter Minimum window co-ordinates:- 200 250

Enter Maximum window co-ordinates:- 300 350

Enter co-ordinates of first point of line: - 180 250

Enter co-ordinates of second point of line: - 200 300

Algorithm: Sutherland-Hodgeman algorithm

1. Input Coordinates of all vertices of the polygon

2. Input coordinates of the clipping window

3. Consider the left edge of the window

4. Compare the vertices of each edge of the polygon, individually with the clipping plane

5. Save the resulting intersections and vertices in the new list of vertices according to four possible

relationships between the edge and the clipping boundary discussed earlier

6. Repeat the steps 4 and 5 for remaining edges of the clipping window. Each time the resultant list of vertices

is successively passed to process the next edge of the clipping window

7. Stop


1. Explain why Sutherland-Hodgeman algorithm works only for convex clipping regions?

Evaluation Policy:





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Lab Assignment 11: Curve Generation

Objective:

To study and Implement Curves Generation using Bezeir Curves.

Reference:


Prerequisite:

Knowledge of:

Bezier Curve

Academic Honesty:






student.












You have to design a program which will take input of the coordinates of control point which is also determined

from user input. Then you have to draw the curve using the following algorithm. Like,

Enter the no. of control points: 3

Enter the control point1:- 20 50


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Algorithm: Bezier Curve

1. Get Three control points say A(x A , yA ), B(x B , yB), C(xC , yC)

2. Divide the curves represented by point A,B,C

x AB = (xA + xB ) / 2

y AB = (yA + yB ) / 2

xBC = (xB+ xC ) / 2

yBC = (yB+ yC ) / 2

xABC = (xAB + xBC ) / 2

yABC = (yAB + yBC ) / 2

3. Repeat the step 2 for section A AB, ABC

4. Repeat step 3 until we have sections so short that they can be replaced by straight lines

5. Replace small sections by straight lines

6. Stop


Now implement the above curve by getting control points from mouse click that means each mouse click will

supply the coordinates of the control points.

Evaluation Policy:





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Lab Assignment 12: Lighting in OpenGL

Objective:

1. Understand how real-world lighting conditions are approximated by OpenGL

2. Render illuminated objects by defining light source, material, and lighting model properties

Reference:

1. OpenGL Programming Guide, Red Book

Prerequisite:

Knowledge of:

Basic Lighting and shading

Academic Honesty:






student.











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You have to design a program in which you have to draw a solid sphere and place three light sources from three

directions and those colors should be Red, Green and Blue.

Example code: A Lit Sphere

void init(void)

{

GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };

GLfloat mat_shininess[] = { 50.0 };

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

GLfloat white_light[] = { 1.0, 1.0, 1.0, 1.0 };

GLfloat lmodel_ambient[] = { 0.1, 0.1, 0.1, 1.0 };

glClearColor(0.0, 0.0, 0.0, 0.0);

glShadeModel(GL_SMOOTH);

glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);

glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);

glLightfv(GL_LIGHT0, GL_POSITION, light_position);

glLightfv(GL_LIGHT0, GL_DIFFUSE, white_light);

glLightfv(GL_LIGHT0, GL_SPECULAR, white_light);

glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient);

glEnable(GL_LIGHTING);

glEnable(GL_LIGHT0);

glEnable(GL_DEPTH_TEST);

}

void display(void)

{

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glutSolidSphere(1.0, 20, 16);

glFlush();

}

void reshape(int w, int h)

{

glViewport(0, 0, (GLsizei) w, (GLsizei) h);


glLoadIdentity();

if (w

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1. Implement a light source into a triangle and rectangle.

Evaluation Policy:





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Lab Assignment 13: Color in OpenGL

Objective:

To study and Implement Colors and shading, using color index in OpenGL

Reference:

1. OpenGL Programming Guide, Red book

Prerequisite:

Knowledge of:

Color model, color space

Academic Honesty:






student.











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You have to design a program which will produce colored rectangles of variation of RGB colors with all

possible combination of RGB within a range of .05

Example code: Smooth Shaded Triangle

void init(void)

{

glClearColor(0.0, 0.0, 0.0, 0.0);

glShadeModel(GL_SMOOTH);

}

void triangle(void)

{ glBegin(GL_TRIANGLES);

glColor3f(1.0, 0.0, 0.0);

glVertex2f(5.0, 5.0);

glColor3f(0.0, 1.0, 0.0);


glColor3f(0.0, 0.0, 1.0);


glEnd();

}

void display(void)

{

glClear(GL_COLOR_BUFFER_BIT);

triangle();

glFlush();

}

void reshape(int w, int h)

{

glViewport(0, 0, (GLsizei) w, (GLsizei) h);


glLoadIdentity();

if (w

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Lab Assignment 14: Animation

Objective:

To implement a program with animation of objects (segments) obtained by scan conversion.

Reference:


Prerequisite:

Knowledge of:

All Raster Scan Algorithms

o Segmentation and its properties

Academic Honesty:






student.











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Description:

Animation:

Sequences of pictures at educate or explain may require images of 3D objects. Although animation uses

graphics as much for art as for realism, it depends heavily on motions to substitute for realism of an individual

image. Animation is done by photographing a sequence of drawings, each slightly different from the previous.

This can be achieved by segmentation.

For example to show a person moving his arm, a series of drawings is photographed, each drawing showing the

arm at a different position. When the images are displayed one after another from the frame buffer, we perceive

the arm as moving through the sequence.


1. How renaming operations of segments is useful for animation?

2. What do you mean by posting and unposting of segments?

3. Explain the use of display and segmentation in graphics.

Evaluation Policy:





lab manual final computer graphics

Documents

lab classes

opengl programming structure

opengl programming guide

opengl programming objective

graphics window reference

line drawing algorithm

opengl utility toolkit

circle drawing algorithm