Aim:

Program to display a set of values {fij} as a rectangular mesh.

Algorithm :

1. Define two variables maxx and maxy for the sides of the rectangular mesh.
2. Define dx,dy and also define two arrays x and y.
3. Under init() , we call glLoadIdentity() to start over from the origin.
4. In the display function , you run for loops that update the arrays with (x[i],y[j]) positions.
5. Display the rectangular mesh by passing GL_LINE_LOOP to glBegin as a parameter.

Code: rectMesh.c

#include<stdio.h>
#include<stdlib.h>
#include<GL/glut.h>
#define maxx 20
#define maxy 25
#define dx 10
#define dy 15
GLfloat x[maxx]={0.0},y[maxy]={0.0};
GLfloat x0=50,y0=50;
GLint i,j;

void init()
{
    glClearColor(1.0,1.0,1.0,1.0);
    glPointSize(5.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0,499.0,0.0,499.0);
    glutPostRedisplay();
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    for(i=0;i<maxx;i++)
        x[i]=x0+i*dx;
    for(j=0;j<maxy;j++)
        y[j]=y0+j*dy;
    for(i=0;i<maxx-1;i++)
        for(j=0;j<maxy-1;j++)
        {
            glColor3f(0.0,0.0,1.0);
            glBegin(GL_LINE_LOOP);
                glVertex2f(x[i],y[j]);
                glVertex2f(x[i],y[j+1]);
                glVertex2f(x[i+1],y[j+1]);
                glVertex2f(x[i+1],y[j]);
            glEnd();
        }
    glFlush();
}

int main(int argc,char **argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutInitWindowSize(500,400);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Rectangular Mesh");
    glutDisplayFunc(display);
    init();
    glutMainLoop();
}

Output:

Commands for execution:-

• Open a terminal and Change directory to the file location in both the terminals.
• compile as gcc -lGLU -lGL -lglut rectMesh.c -o mesh
• If no errors, run as ./mesh

Screenshots:-