Sem 4‎ > ‎CG LAB‎ > ‎

Q12: WAP to perform rotation wrt to a point.

posted Mar 4, 2012, 8:23 AM by Neil Mathew   [ updated Mar 6, 2012, 7:36 AM ]


SOURCE CODE:

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#include<iostream.h>
#include<conio.h>
#include<graphics.h>
#include<math.h>
 
int n;
double P[3][10];
double P2[3][10];
 
double S[3][3];
double angle;
int h,k;
 
double deg2rad(double deg)
{
   double rad= ((22.0/7.0)/180.0)*deg;
   return rad;
 
}
 
 
void INPUT()
{
int ch;
cout<<"\n For Polygon where No of edges (>3) = ";
cin>>n;
 
cout<<"\n Enter the coordinates of "<<n<<" sided Polygon: \n";
 
for(int i=0; i<n; i++)
{
cout<<" "<<i+1<<" Point (x,y) : ";
cin>>P[0][i]>>P[1][i];
P[2][i]=1;
}
 
cout<<"\n Enter the Angle: "; cin>>angle;
 
cout<<"\n Scaling W.R.T which point (1/2/3...) : ";
cin>>ch;
 
if(ch!=0)
{
h=P[0][ch-1];
k=P[1][ch-1];
}
}
 
 
void ROTATEpoint()
{
                   double x=angle;
// S[3][3] : Scaling MATRIX
// P[3][n] : 3 x n MATRIX
// P2[3][n] : Final MATRIX
 
//ROTATE Matrix:
//1st - making the identity Matrix
for(int i=0; i<3; i++)
{
for(int j=0; j<3; j++)
{
        if(i==j)     //DIAGONAL
        S[i][j] = 1;
        else
        S[i][j] = 0;
}
}
//2nd - making changes
S[0][0] = cos (  deg2rad(x) );
S[0][1] = - sin( deg2rad(x) );
S[1][0] = sin ( deg2rad(x) );
S[1][1] = cos ( deg2rad(x) );
 
S[0][2] = -h*cos(deg2rad(x)) + k*sin ( deg2rad(x) ) + h;
S[1][2] = -h*sin(deg2rad(x)) - k*cos ( deg2rad(x) ) + k;
 
 
 
// Matrix Multiplication
// S(3x3)  x  P(3xN)
 
for(i=0; i<3; i++)
{
for(int j=0; j<n; j++)
{
        P2[i][j]=0;
for(int k=0; k<3; k++)
{
P2[i][j]+=S[i][k]*P[k][j];
}
}
}
 
}
 
void Display_Matrix(double p[3][10])
{
 
for(int i=0; i<3; i++)
{
cout<<"\n |";
for(int j=0; j<n; j++)
cout<<"  "<<p[i][j];
cout<<"  |";
}
 
}
 
void DRAW(double p[3][10])
{
 
for(int i=0; i<n-1; i++)
{
line(getmaxx()*0.5+p[0][i], getmaxy()*0.5+p[1][i], 
               getmaxx()*0.5+p[0][i+1], getmaxy()*0.5+p[1][i+1]);
} line(getmaxx()*0.5+p[0][n-1], getmaxy()*0.5+p[1][n-1],                     getmaxx()*0.5+p[0][0], getmaxy()*0.5+p[1][0]);   }     void main() { INPUT(); Display_Matrix(P); cout<<endl;   ROTATEpoint();   for(int i=0; i<3; i++) { cout<<"\n |"; for(int j=0; j<3; j++) cout<<" "<<S[i][j]; cout<<" |"; } cout<<endl;   Display_Matrix(P2);   cout<<"\n\n Press Enter to see Graphically? "; getch();   int gdriver=DETECT,gmode; initgraph(&gdriver,&gmode,"C:/TC/BGI");     setcolor(DARKGRAY); //X AXIS line(getmaxx()*0.5, 0, getmaxx()*0.5, getmaxy()); //Y AXIS line(0, getmaxy()*0.5, getmaxx(), getmaxy()*0.5);     setcolor(CYAN); DRAW(P); setcolor(GREEN); DRAW(P2);   getch(); closegraph();   }



OUTPUT:




(NOT w.r.t. a point)


The images below are inaccurate. My Degree to Radian formula was faulty when I took these. The above program should yield more proper angles where the rotation takes place ANTI CLOCKWISE unlike the clockwise ones below.






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