t2d.c

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/*
** ---------------------------------------------------------------
** t2d.c  -  Module to manage 2D matrix transformations.
**
** ---------------------------------------------------------------
*/

/*
** ---------------------------------------------------------------
** Global variables and symbols:
*/
#include <math.h>
#include "t2d.h"

/*
** ---------------------------------------------------------------
** Local variables and symbols:
*/
#ifndef rad
#define rad(a)  ((a)*(double)0.01745329252)
#endif

typedef double Matrix2d[2][3];

static Matrix2d mt =
 {
  { 1.0, 0.0, 0.0 },
  { 0.0, 1.0, 0.0 }
 };

/*
** ---------------------------------------------------------------
** Local functions:
*/

/*=======================  t2dAccumulate  ======================*/
static void t2dAccumulate( Matrix2d nmt )
{
 double   t;

 t        =  mt[0][0]*nmt[0][0] + mt[1][0]*nmt[0][1];
 mt[1][0] =  mt[0][0]*nmt[1][0] + mt[1][0]*nmt[1][1];
 mt[0][0] =  t;

 t        =  mt[0][1]*nmt[0][0] + mt[1][1]*nmt[0][1];
 mt[1][1] =  mt[0][1]*nmt[1][0] + mt[1][1]*nmt[1][1];
 mt[0][1] =  t;

 t        =  mt[0][2]*nmt[0][0] + mt[1][2]*nmt[0][1] + nmt[0][2];
 mt[1][2] =  mt[0][2]*nmt[1][0] + mt[1][2]*nmt[1][1] + nmt[1][2];
 mt[0][2] =  t;
}

/*
** ---------------------------------------------------------------
** Public functions:
*/

/*======================  t2dTransform  ========================*/
void t2dTransform( double *x, double *y )
{
 double t;
  t = (*x)*mt[0][0] + (*y)*mt[0][1] + mt[0][2];
 *y = (*x)*mt[1][0] + (*y)*mt[1][1] + mt[1][2];
 *x = t;
}

/*======================  t2dIdentity  =========================*/
void t2dIdentity( void )
{
 mt[0][0] = 1.0; mt[0][1] = 0.0; mt[0][2] = 0.0;
 mt[1][0] = 0.0; mt[1][1] = 1.0; mt[1][2] = 0.0;
}

/*=======================  t2dTranslate  =======================*/
void t2dTranslate( double dx, double dy )
{
 Matrix2d trl;

/**** COMPLETE AQUI: 014 ****/

 t2dAccumulate( trl );
}

/*=========================  t2dScale  =========================*/
void t2dScale( double sx, double sy )
{
 Matrix2d scl;

/**** COMPLETE AQUI: 015 ****/

 t2dAccumulate( scl );
}

/*=======================  t2dScaleAbout  ======================*/
void t2dScaleAbout( double cx, double cy, double sx, double sy )
{
 t2dTranslate( -cx, -cy );
 t2dScale( sx, sy );
 t2dTranslate( cx, cy );
}

/*=========================  t2dRotate  ========================*/
void t2dRotate( double angle )
{
 double cost = cos(rad(angle));
 double sint = sin(rad(angle));
 Matrix2d rot;

/**** COMPLETE AQUI: 016 ****/

 t2dAccumulate( rot );
}

/*======================  t2dRotateAbout  ======================*/
void t2dRotateAbout( double cx, double cy, double angle )
{
 t2dTranslate( -cx, -cy );
 t2dRotate( angle );
 t2dTranslate( cx, cy );
}

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