## bookmark_borderMatrix in OpenGL

[0  4  8 12]
[1  5  9 13]
[2  6 10 14]
[3  7 11 15]

4x4 matrix in memory.

[R0 R3 R6 Tx]
[R1 R4 R7 Ty]
[R2 R5 R8 Tz]
[ 0  0  0  1]

‘R’ represents rotations and scaling (and shearing)
‘T’ translation

First, I read the matrix and print it.

float x[16];
int i;

//read the 4x4 matrix and store in x
glGetFloatv (GL_MODELVIEW_MATRIX, (float*)x);

//print the matrix
for(i=0; i

## bookmark_borderSimple Solar System in OpenGL

I have created a simple Solar System using OpenGL

#include <stdlib.h>
#include <GLUT/glut.h>
#include <math.h>
#include <stdio.h>

static float Xvalue = 0.0, Yvalue = 0.0, Angle = 0.0;

int MoveX = 0;
int MoveY = 0;

void myInit(void) {
glClearColor (0.0, 0.0, 0.0, 0.0);
}

static float x1[360][2];
static float x2[360][2];
static float x3[720][2];

void generateCircle()
{
int i = 0;

for(i=0; i <= 360; i++)
{
x1[i][0] = sin(i*3.1416/180)*3;
x1[i][1] = cos(i*3.1416/180)*3;
}

for(i=0; i <= 360; i++)
{
x2[i][0] = sin(i*3.1416/180)*1;
x2[i][1] = cos(i*3.1416/180)*1;
}

for(i=0; i <= 720; i++)
{
x3[i][0] = sin(i*3.1416/180)*5;
x3[i][1] = cos(i*3.1416/180)*5;
}

}

void myDisplay(void) {

glClear (GL_COLOR_BUFFER_BIT);
glColor3f (1.0, 1.0, 1.0);

//sun
glPushMatrix();
gluLookAt (0.0, 10.0, 2.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0);
glTranslatef(Xvalue, 0.0, Yvalue);
glRotatef(Angle, 0.0, 0.0, 1.0);
glutWireSphere (0.5, 15, 15);
glPopMatrix();

glPushMatrix();
gluLookAt (0.0, 10.0, 2.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0);
if(MoveX==360)
MoveX = 0;
glTranslatef(x1[MoveX][1], x1[MoveX][0], 0.0);
glRotatef(Angle, 0.0, 0.0, 1.0);
glutWireSphere (0.4, 15, 15);
glTranslatef(x2[MoveX][0], x2[MoveX][1], 0.0);
glutWireSphere (0.2, 15, 15);
glPopMatrix();

glPushMatrix();
gluLookAt (0.0, 10.0, 2.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0);
if(MoveY==720)
MoveY = 0;
glTranslatef(x3[MoveY/2][1], x3[MoveY/2][0], 0.0);
glRotatef(Angle, 0.0, 0.0, 1.0);
glutWireSphere (0.4, 15, 15);
int i = 0;
//glBegin(GL_LINE_STRIP);
for(i=0; i <= 360; i++)
{
glVertex3f(sin(i*3.1416/180)*0.5, cos(i*3.1416/180)*0.5, 0 );
glVertex3f(sin(i*3.1416/180)*0.7, cos(i*3.1416/180)*0.7, 0 );
}
glEnd();
glRotatef(Angle, 0.0, 0.0, 1.0);
glPopMatrix();

glFlush ();
}

void resize(int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glFrustum (-1.0, 1.0, -1.0, 1.0, 1.5, 20.0);
glMatrixMode (GL_MODELVIEW);
}

void animation()
{
Angle += 15.0;
glutPostRedisplay();
MoveX +=1;
MoveY +=1;
glutPostRedisplay();
glutTimerFunc(100, animation, 0);

}

int main(int argc, char ** argv){

glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(1024, 768);
glutInitWindowPosition(100, 150);
glutCreateWindow("OpenGL");
myInit();
glutDisplayFunc(myDisplay);
glutReshapeFunc(resize);
generateCircle();
glutTimerFunc(100, animation, 0);
glutMainLoop();
}