www.pudn.com > CG2Programs.rar > transformObject2.c

/* transformObject chap. 5, pp. 199-200 */

/* EXAMPLE STARTS HERE */
#include 
#include "graphics.h"

typedef float Matrix3x3[3][3];
Matrix3x3 theMatrix;

void matrix3x3SetIdentity (Matrix3x3 m)
{
  int i,j;

  for (i=0; i<3; i++) for (j=0; j<3; j++) m[i][j] = (i == j);
}

/* Multiplies matrix a times b, putting result in b */
void matrix3x3PreMultiply (Matrix3x3 a, Matrix3x3 b)
{
  int r,c;
  Matrix3x3 tmp;

  for (r = 0; r < 3; r++)
    for (c = 0; c < 3; c++)
      tmp[r][c] =
	a[r][0]*b[0][c] + a[r][1]*b[1][c] + a[r][2]*b[2][c];

  for (r = 0; r < 3; r++)
    for (c = 0; c < 3; c++)
      b[r][c] = tmp[r][c]; 
}

void translate2 (int tx, int ty)
{
  Matrix3x3 m;

  matrix3x3SetIdentity (m);
  m[0][2] = tx;
  m[1][2] = ty;
  matrix3x3PreMultiply (m, theMatrix);
}

void scale2 (float sx, float sy, wcPt2 refpt)
{
  Matrix3x3 m;

  matrix3x3SetIdentity (m);
  m[0][0] = sx; 
  m[0][2] = (1 - sx) * refpt.x;
  m[1][1] = sy; 
  m[1][2] = (1 - sy) * refpt.y;
  matrix3x3PreMultiply (m, theMatrix);
}

void rotate2 (float a, wcPt2 refPt)
{
  Matrix3x3 m;

  matrix3x3SetIdentity (m);
  a = pToRadians (a);
  m[0][0] = cosf (a);
  m[0][1] = -sinf (a);
  m[0][2] = refPt.x * (1 - cosf (a)) + refPt.y * sinf (a);
  m[1][0] = sinf (a);
  m[1][1] = cosf (a);
  m[1][2] = refPt.y * (1 - cosf (a)) - refPt.x * sinf (a);
  matrix3x3PreMultiply (m, theMatrix);
}

void transformPoints2 (int npts, wcPt2 *pts)
{
  int k;
  float tmp;
  
  for (k = 0; k < npts; k++) {
    tmp = theMatrix[0][0] * pts[k].x + theMatrix[0][1] * 
      pts[k].y + theMatrix[0][2];
    pts[k].y = theMatrix[1][0] * pts[k].x + theMatrix[1][1] * 
      pts[k].y + theMatrix[1][2];
    pts[k].x = tmp;
  }
}

void main (int argc, char ** argv)
{
  wcPt2 pts[3] = { 50.0, 50.0, 150.0, 50.0, 100.0, 150.0};
  wcPt2 refPt = {100.0, 100.0};
  long windowID = openGraphics (*argv, 200, 350);
  
  setBackground (WHITE);
  setColor (BLUE);
  pFillArea (3, pts);
  matrix3x3SetIdentity (theMatrix);
  scale2 (0.5, 0.5, refPt);
  rotate2 (90.0, refPt);
  translate2 (0, 150);
  transformPoints2 (3, pts);
  pFillArea (3,pts);
  sleep (10);
  closeGraphics (windowID);
}
/* EXAMPLE ENDS HERE */