Solved

MAKING TRANSFORMATIONS USING BORLAND C++

Posted on 2004-03-25
7
435 Views
Last Modified: 2008-02-20
can anyone help me, please
how can I make some transformations "like translation,
scaling, rotation, ...." using the Borland C++ 3.1
Graphics Package?

thanks
ARSSES.  
0
Comment
Question by:ARSSES
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
7 Comments
 
LVL 9

Accepted Solution

by:
ankuratvb earned 25 total points
ID: 10683394
Hi,

This code performs all 2D tranformations and this works till four vertex figures.
Enter the co-ordinates in clockwise order.

//2D Transformations
#include<math.h>
#include<iostream.h>
#include <graphics.h>
#include <conio.h>
#include<dos.h>

float r2d=M_PI/180.0f;
float co[4][3];
float tr[3][3];
float res[4][3]={0};
int r=4,c=3,n;
void draw(int);
void disp();
void rotate(int,int,float);
void translate(int,int);
void scale(int,int);
void matmul();
int main()
{
      int gdriver = DETECT, gmode;
      int i,j;
      cout<<"Enter the no. of pts:";
      cin>>n;
      cout<<"Enter the Pairs of co-ordinates:\n";
      for(i=0;i<n;i++)
      {
       cin>>co[i][0]>>co[i][1];
       co[i][2]=1;
      }
      initgraph(&gdriver, &gmode, "\\tc\\bgi");
      cleardevice();
      draw(1);
      getch();
      //scale(4,4);
      //translate(100,100);
      //draw(15);
      //getch();
      //scale(2,2);

      rotate(0,0,45.0f);
      disp();
      draw(15);
      getch();
      closegraph();
      return 0;
}
void disp()
{
      int i,j;
      for(i=0;i<n;i++)
      {
       for(j=0;j<3;j++)
       {
        cout<<co[i][j]<<" ";
       }
       cout<<"\n";
      }
}
void draw(int col)
{
 int i,j;
 setcolor(col);
/*
 for(i=0;i<n;i++)
 {
  circle(co[i][0],co[i][1],5);
 }
*/
 for(i=0;i<n;i++)
 {
  if(i==n-1) j=0; else j=i+1;
  line(co[i][0],co[i][1],co[j][0],co[j][1]);
 }
}
void translate(int tx,int ty)
{
 int i;
 for(i=0;i<3;i++)
 {tr[i][i]=1;}
 tr[0][1]=0;tr[0][2]=0;
 tr[1][0]=0;tr[1][2]=0;
 tr[2][0]=tx;tr[2][1]=ty;
 matmul();
}

void scale(int sx,int sy)
{
 tr[0][0]=sx;tr[1][1]=sy;tr[2][2]=1;
 tr[0][1]=0;tr[0][2]=0;
 tr[1][0]=0;tr[1][2]=0;
 tr[2][0]=0;tr[2][1]=0;
 matmul();
}

void rotate(int x,int y,float th)
{
 //translate(-x,-y);
 float ang=th*r2d;
 tr[0][0]=cos(ang);tr[1][1]=cos(ang);tr[2][2]=1;
 tr[0][1]=sin(ang);tr[0][2]=0;
 tr[1][0]=-sin(ang);tr[1][2]=0;
 tr[2][0]=0;tr[2][1]=0;
 matmul();
 //translate(x,y);
}
void matmul()
{
 int i,j,k;
 for(i=0;i<r;i++)
  {
  for(j=0;j<c;j++)
  {
   for(k=0;k<c;k++)
   {
    res[i][j]=res[i][j]+(co[i][k]*tr[k][j]);
   }
  }
 }
for(i=0;i<n;i++)
{
 for(j=0;j<3;j++)
 {
  co[i][j]=res[i][j];
 }
}
}
0
 
LVL 2

Assisted Solution

by:Avik77
Avik77 earned 25 total points
ID: 10683408
u must be following some standard graphics algorithms for these. Most of them generally represent the co-ordinates of an arbitrary figure as a matrix and apply different matrix transformations to achieve different configurations of the figures.U can also find some important stuff here
 http://alumni.imsa.edu/~stendahl/comp/links.html
Try them.

Avik.
0
 
LVL 9

Expert Comment

by:ankuratvb
ID: 10685946
Hi,

All these transformations i.e. translation,scaling and rotation have standard matrices that
are used.
Just do a Google for :2D transformations "computer graphics"

U'll get plenty of links and there are a number of standard matrices that are used by dif.
authors.

Some represent the matrices as row matrices,some as column matrices.

In my program ,i have used the fol. matrix format
x' and y' are the co-ordinates after tranformations
x and y are the co-ordinates before tranformations.

Matrices of 3 columns(why the extra 1?u could have asked) have been used for 2D to make the co-ordinates homogeneous i.e. all the operations can be represented as matrix multiplications


[x' y' 1]=[x y 1][1 0 0
                         0 1 0
                        tx ty 1]

For translation where tx and ty are the translation displacements respectively.

[x' y' 1]=[x y 1][sx  0 0
                         0  sy 0
                         0   0  1]

For scaling where sx and sy are the scale ratios in x and y respectively.

[x' y' 1]=[x y 1][cos a  sin a  0
                         -sin a cos a  0
                           0        0      1]

For rotation where a is the angle in degrees and this is rotation anti-clockwise.
For clockwise,replace a by -a

So,if u have a number of points say 3 points,
store them in matrix as:
[x1 y1 1
 x2 y2 1
 x3 y3 1]
and multiply this matrix with the appropriate transformation matrix to get the new co-ordinates.


HTH
0
 

Author Comment

by:ARSSES
ID: 10709971
HI,

I WNTA TO SAY THANKS FOR ANKURATUB & AVIK77
 FOR HELPING ME "MANY THANKS".

ARSSES
0
 
LVL 9

Expert Comment

by:ankuratvb
ID: 10709988
Glad to be of help.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

This tutorial is posted by Aaron Wojnowski, administrator at SDKExpert.net.  To view more iPhone tutorials, visit www.sdkexpert.net. This is a very simple tutorial on finding the user's current location easily. In this tutorial, you will learn ho…
This is a short and sweet, but (hopefully) to the point article. There seems to be some fundamental misunderstanding about the function prototype for the "main" function in C and C++, more specifically what type this function should return. I see so…
The goal of this video is to provide viewers with basic examples to understand opening and writing to files in the C programming language.
The goal of this video is to provide viewers with basic examples to understand how to use strings and some functions related to them in the C programming language.

752 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question