Projection of a CUBE using OpenGL in C++

Using OpenGL Library in C++ to projecting the cube. Projection mean show 3D points in 2D plan.

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#include 
#include
#include
#include

int WinWidth = 500, WinHeight = 500;

typedef struct{float x;float y;}Point2D;
typedef struct{float x;float y;float z;}Point3D;

Point3D COP = {0,0,-200}; // Centre Of Projection is at (0,0,-200)

Point3D A,B,C,D,E,F,G,H,I,J; // Vertices of the cube

Point2D Projected_A,Projected_B,Projected_C,Projected_D,Projected_E,Projected_F,Projected_G,Projected_H,Projected_I,Projected_J;

void constructBarn(){
A.x = 200; A.y = 100; A.z = 200;
B.x = 200; B.y = 00; B.z = 200;
C.x = 400; C.y = 00; C.z = 200;
D.x = 400; D.y = 100; D.z = 200;
E.x = 300; E.y = 200; E.z = 200;

F.x = 200; F.y = 100; F.z = 400;
G.x = 200; G.y = 00; G.z= 400;
H.x = 400; H.y = 00; H.z = 400;
I.x = 400; I.y = 100; I.z = 400;
J.x = 300; J.y = 200; J.z = 400;
}

void DrawBarn(Point2D A, Point2D B, Point2D C, Point2D D, Point2D E, Point2D F, Point2D G, Point2D H, Point2D I, Point2D J){
glPointSize(1.0);

glBegin(GL_LINE_LOOP);
//DRAWING FRONT FACE
glVertex2i(A.x, A.y);
glVertex2i(B.x, B.y);
glVertex2i(C.x, C.y);
glVertex2i(D.x, D.y);
glVertex2i(E.x, E.y);

glEnd();

glBegin(GL_LINE_LOOP);
//DRAWING BACK FACE
glVertex2i(F.x, F.y);
glVertex2i(G.x, G.y);
glVertex2i(H.x, H.y);
glVertex2i(I.x, I.y);
glVertex2i(J.x, J.y);

glEnd();

glBegin(GL_LINES);

//DRAWING OTHER LINES
glVertex2i(A.x, A.y);
glVertex2i(F.x, F.y);

glVertex2i(B.x, B.y);
glVertex2i(G.x, G.y);

glVertex2i(C.x, C.y);
glVertex2i(H.x, H.y);

glVertex2i(D.x, D.y);
glVertex2i(I.x, I.y);

glVertex2i(E.x, E.y);
glVertex2i(J.x, J.y);

glEnd();

glFlush();
}


Point2D Project_Perspective(Point3D p, Point3D CoP){
Point2D p2;
float d = abs(CoP.z); // The distance between the COP and orign

p2.x = d*(p.x)/(p.z+d);
p2.y = d*(p.y)/(p.z+d);

//.....wite necessary equations here for perspective transformation

return p2;
}


Point2D translate2D(Point2D p, float tx, float ty){
Point2D tp2;
tp2.x = p.x + tx;
tp2.y = p.y + ty;

return tp2;
}

Point3D translate3D(Point3D p, float tx, float ty, float tz){
Point3D tp3;
//.....wite the equations for 3D translation
tp3.x = p.x + tx;
tp3.y = p.y + ty;
tp3.z = p.z + tz;
return tp3;
}

Point3D scaling3D(Point3D p, float Sx, float Sy, float Sz){
Point3D tp4;

tp4.x = p.x*Sx;
tp4.y = p.y*Sy;
tp4.z = p.z*Sz;
return tp4;
}

void resize(float Sx,float Sy,float Sz){
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0f, 0.0f, 0.0f);

//scale the point
A = scaling3D(A,Sx,Sy,Sz);
B = scaling3D(B,Sx,Sy,Sz);
C = scaling3D(C,Sx,Sy,Sz);
D = scaling3D(D,Sx,Sy,Sz);
E = scaling3D(E,Sx,Sy,Sz);
F = scaling3D(F,Sx,Sy,Sz);
G = scaling3D(G,Sx,Sy,Sz);
H = scaling3D(H,Sx,Sy,Sz);
I = scaling3D(I,Sx,Sy,Sz);
J = scaling3D(J,Sx,Sy,Sz);

//Do projection
Projected_A = Project_Perspective(A,COP);
Projected_B = Project_Perspective(B,COP);
Projected_C = Project_Perspective(C,COP);
Projected_D = Project_Perspective(D,COP);
Projected_E = Project_Perspective(E,COP);
Projected_F = Project_Perspective(F,COP);
Projected_G = Project_Perspective(G,COP);
Projected_H = Project_Perspective(H,COP);
Projected_I = Project_Perspective(I,COP);
Projected_J = Project_Perspective(J,COP);


DrawBarn(
// Calculate the following values
Projected_A,
Projected_B,
Projected_C,
Projected_D,
Projected_E,
Projected_F,
Projected_G,
Projected_H,
Projected_I,
Projected_J
);

}

void keyboard(unsigned char key, int x, int y)
{
if (key == 'q' || key == 'Q')
exit(EXIT_SUCCESS);

if(key == '+')
resize(2,2,2);

if(key == '-')
resize(0.5,0.5,0.5);

}

void myMouse(int button, int state, int x, int y) {
if(state == GLUT_DOWN)
{
if(button == GLUT_LEFT_BUTTON)
{

}
else if (button == GLUT_RIGHT_BUTTON)
{

}
}
}

void myDisplay()
{
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0f, 0.0f, 0.0f);

Projected_A = Project_Perspective(A,COP);
Projected_B = Project_Perspective(B,COP);
Projected_C = Project_Perspective(C,COP);
Projected_D = Project_Perspective(D,COP);
Projected_E = Project_Perspective(E,COP);
Projected_F = Project_Perspective(F,COP);
Projected_G = Project_Perspective(G,COP);
Projected_H = Project_Perspective(H,COP);
Projected_I = Project_Perspective(I,COP);
Projected_J = Project_Perspective(J,COP);



DrawBarn(
// Calculate the following values
Projected_A,
Projected_B,
Projected_C,
Projected_D,
Projected_E,
Projected_F,
Projected_G,
Projected_H,
Projected_I,
Projected_J
);


}


int main( int argc, char ** argv ) {
glutInit( &argc, argv );
glutInitWindowPosition( 0, 0 );
glutInitWindowSize( WinWidth, WinHeight );
glutCreateWindow( "Projection of a Cube" );

glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluOrtho2D( 0, WinWidth, 0, WinHeight );
glViewport(0, 0, WinWidth, WinHeight);

constructBarn();

glutKeyboardFunc(keyboard);
glutMouseFunc( myMouse );
glutDisplayFunc( myDisplay );
glutMainLoop();

return( 0 );
}
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