Introduction to Computer Graphics using OpenGL Can someone tell me what shall I
ID: 3801119 • Letter: I
Question
Introduction to Computer Graphics using OpenGL
Can someone tell me what shall I do to connect between the LineClipping, drawing the line, and rectangle function? I wrote the code below for the above question:
#include<GL/glut.h>
#define red makecol(255,0,0)
#define green makecol(0,255,0)
#include <windows.h> // use as needed for your system
#include <math.h>
#include <gl/Gl.h>
#include <gl/glut.h>
#include <iostream>
#include "vector.h"
const int screenWidth = 800;
const int screenHeight = 600;
double xmax, xmin, ymax, ymin;
typedef int OutCode;
double xvmin, yvmin, xvmax, yvmax;
int clicks = 0;
Point positions[4];
bool flag = false;
const int INSIDE = 0; // 0000
const int LEFT = 1;
const int RIGHT = 2;
const int BOTTOM = 4; // 0100
const int TOP = 8;
OutCode ComputeOutCode(double x, double y)
{
OutCode code;
code = INSIDE;
if (x < xmin)
code |= LEFT;
else if (x > xmax)
code |= RIGHT;
if (y < ymin)
code |= BOTTOM;
else if (y > ymax)
code |= TOP;
return code;
}
void LineClipping(double x0, double y0, double x1, double y1)
{
OutCode outcode0 = ComputeOutCode(x0, y0);
OutCode outcode1 = ComputeOutCode(x1, y1);
bool accept = false; bool done = false;
while (done)
{
if (!(outcode0 | outcode1)) // Trivially accept and get out of loop
{
accept = true; done = true;
break;
}
else if (outcode0 & outcode1) // Trivially reject and get out of loop
{
done = true;
break;
}
else
{
// failed both tests, so calculate the line segment to clip
// from an outside point to an intersection with clip edge
double x, y;
// At least one endpoint is outside the clip rectangle; pick it.
OutCode outcodeOut = outcode0 ? outcode0 : outcode1;
// Now find the intersection point;
if (outcodeOut & TOP) { // point is above the clip rectangle
x = x0 + (x1 - x0) * (ymax - y0) / (y1 - y0);
y = ymax;
}
else if (outcodeOut & BOTTOM) { // point is below the clip rectangle
x = x0 + (x1 - x0) * (ymin - y0) / (y1 - y0);
y = ymin;
}
else if (outcodeOut & RIGHT) { // point is to the right of clip rectangle
y = y0 + (y1 - y0) * (xmax - x0) / (x1 - x0);
x = xmax;
}
else if (outcodeOut & LEFT) { // point is to the left of clip rectangle
y = y0 + (y1 - y0) * (xmin - x0) / (x1 - x0);
x = xmin;
}
if (outcodeOut == outcode0)
{
x0 = x;
y0 = y;
outcode0 = ComputeOutCode(x0, y0);
}
else {
x1 = x;
y1 = y;
outcode1 = ComputeOutCode(x1, y1);
}
}
}
if (accept)
{
// window to viewport mapping
/* double sx = (xvmax - xvmin) / (xmax - xmin);// scale parameter in x direction
double sy = (yvmax - yvmin) / (ymax - ymin);// scale parameter in y direction
double vx0 = xvmin + (x0 - xmin)*sx;
double vy0 = yvmin + (y0 - ymin)*sy;
double vx1 = xvmin + (x1 - xmin)*sx;
double vy1 = yvmin + (y1 - ymin)*sy;*/
//draw a red color viewport
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINE_LOOP);
glVertex2f(xmin, ymin);
glVertex2f(xmax, ymin);
glVertex2f(xmax, ymax);
glVertex2f(xmin, ymax);
glEnd();
glColor3f(0.0, 0.0, 1.0);
glBegin(GL_LINES);
glVertex2d(x0, y0);
glVertex2d(x1, y1);
glEnd();
}
}
//<<<<<<<<<<<<<<<<<<<<<<< myInit >>>>>>>>>>>>>>>>>>>>
void myInit(void)
{
glClearColor(1.0, 1.0, 1.0, 0.0); // set white background color
glColor3f(0.4f, 0.7f, 0.2f); // set the drawing color
glPointSize(8.0); // a ‘dot’ is 4 by 4 pixels
}
void setWindow(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(left, right, bottom, top);
}
// Set the screen viewport using thisfunction
void setViewport(GLint left, GLint right, GLint bottom, GLint top)
{
glViewport(left, bottom, right - left, top - bottom);
}
//<<<<<<<<<<<<<<<<<<<<<<<< myDisplay >>>>>>>>>>>>>>>>>
void myDisplay(void)
{
glClear(GL_COLOR_BUFFER_BIT); // clear the screen
setWindow(0, screenWidth, 0, screenHeight);
setViewport(0, screenWidth, 0, screenHeight);
xmax = double(positions[0].x);
xmin = double(positions[1].x);
ymax = double(positions[0].y);
ymin = double(positions[1].y);
if (clicks >1)
{
{
glBegin(GL_LINE_LOOP);
glVertex2i(positions[0].x, positions[0].y);
glVertex2i(positions[1].x, positions[0].y);
glVertex2i(positions[1].x, positions[1].y);
glVertex2i(positions[0].x, positions[1].y);
glEnd();
}
}
glColor3f(0.0, 1.0, 0.0);
glBegin(GL_LINES);
for (int i = 0; i < clicks; i++)
{
glVertex2i(positions[i].x, positions[i].y);
}
glEnd();
// draw a blue colored window
for (int i = 0; i < clicks; i++)
{
glColor3f(0.0, 0.0, 1.0);
glBegin(GL_POINTS);
glVertex2d(positions[i].x, positions[i].y);
}
glEnd();
glFlush(); // send all output to display
glutSwapBuffers();
}
void myKeyboard(unsigned char key, int x, int y)
{
if (key == 'i')
flag = true;
}
void myMouse(int button, int state, int x, int y)
{
if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
{
if (clicks == 4)
clicks = 0;
positions[clicks] = Point(x, screenHeight - y);
clicks++;
}
if (button == GLUT_MIDDLE_BUTTON && state == GLUT_DOWN)
clicks = 0;
glutPostRedisplay();
}
void main(int argc, char** argv)
{
glutInit(&argc, argv); // initialize the toolkit
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_MULTISAMPLE); // set display mode
glutInitWindowSize(screenWidth, screenHeight); // set window size
glutInitWindowPosition(100, 100); // set window position on screen
glutCreateWindow("cohen sutherland clipping"); // open the screen window
glutDisplayFunc(myDisplay); // register redraw function
glutMouseFunc(myMouse);
//glutMotionFunc(myMouseMove);
//glutKeyboardFunc(myKeyboard);
myInit();
glutMainLoop(); // go into a perpetual loop
}
Explanation / Answer
I will suggest you to go through this code,because the code you have written is very big and the thing with the programming is to write the small codes instead of big ones(which will create confusion).
So here is the code:-
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