Rotation problem

This is a discussion on Rotation problem within the Game Programming forums, part of the General Programming Boards category; Below is the code to rotate a triangle to specified angle but it can't. what is the problem? Code: # ...

  1. #1
    Registered User planet_abhi's Avatar
    Join Date
    Oct 2002
    Posts
    92

    Rotation problem

    Below is the code to rotate a triangle to specified angle but it can't.
    what is the problem?

    Code:
    # include<graphics.h>
    # include<conio.h>
    # include<math.h>
    # include<stdio.h>
    # include<process.h>
    # include<iostream.h>
    # include<dos.h>
    
    float x1=40,y1=360,x2=80,y2=360,x3=60,y3=260;
    
    void dgrid(void);
    void draw_image(int ,int ,int,int,int,int);
    void info(void);
    void trans(void);
    void scale(void);
    void rotate();
    int main()
    {
    int gd=0,gm=0;
    initgraph(&gd,&gm,"e:\\tc\\bgi");
    char ch;
    int flag=0;
    cleardevice();
    draw_image(x1,y1,x2,y2,x3,y3);
    info();
    do
    {
    ch=getch();
    switch(ch)
    {
    case 'T' | 't':
    outtextxy(80,447,"Translate");
    trans();
    break;
    case 'R' | 'r':
    outtextxy(340,447,"   Roatating");
    rotate();
    break;
    case 'S' | 's':
    outtextxy(240,447,"Scaling");
    scale();
    break;
    case 'e' | 'E':
    flag=1;
    break;
    default :
    float tone[7]={130.81,146.83,164.81,174.61,196,220,246.94};
    for(int i=0;i<=7;i++)
    {
    sound(tone[i]*7);
    delay(30);
    }
    nosound();
    }
    }while(flag==0);
    closegraph();
    restorecrtmode();
    return(0);
    }
    void dgrid(void)
    {
    setfillstyle(SOLID_FILL,RED);
    circle(30,400,4);
    floodfill(31,399,15);
    line(30,0,30,420);
    line(10,400,636,400);
    setfillstyle(HATCH_FILL,GREEN);
    floodfill(120,100,WHITE);
    outtextxy(12,370,"Y");
    outtextxy(632,410,"X");
    outtextxy(7,50,"50");
    outtextxy(7,100,"100");
    outtextxy(7,150,"150");
    outtextxy(7,200,"200");
    outtextxy(7,250,"250");
    outtextxy(7,300,"300");
    outtextxy(7,350,"350");
    }
    void draw_image(int a,int b,int c,int d,int e,int f)
    {
    cleardevice();
    dgrid();
    line(a,b,c,d);
    line(c, d, e, f);
    line( a, b, e, f);
    }
    void info()
    {
    outtextxy(59,467,"T : Translate        S : Scale        R : Rotate        E : Exit");
    }
    void trans(void)
    {
    //works
    }
    void scale(void)
    {
    //works
    }
    void rotate()
    {
    int angle;
    outtextxy(340,410,"Enter Angle");
    cin>>angle;
    angle=(angle*3.14)/180;
    x1=x1*cos(angle)+y1*sin(angle);
    y1=-x1*sin(angle)+y1*cos(angle);
    
    x2=x2*cos(angle)+y2*sin(angle);
    y2=-x2*sin(angle)+y2*cos(angle);
    
    x3=x3*cos(angle)+y3*sin(angle);
    y3=-x3*sin(angle)+y3*cos(angle);
    
    draw_image(x1,y1,x2,y2,x3,y3);
    info();
    }

    also i want to get input from user at the bottom of screen what shuold i do?
    AbHHinaay

  2. #2
    ...
    ... is offline
    Registered User
    Join Date
    Feb 2002
    Posts
    465
    i dont know how much this will help, but....

    i was running into a similar problem rotating a bitmap to point at the mouse cursor. i stressed over a solution and had people from all over trying to figure out how to do it.

    then yesterday i was sitting at my computer programming, when it hit me... all of this stuff we were trying to do with vectors and whatever else, i was able to reduce to one line of code.

    Code:
    rotation = - atan2( mouse_y - (screen_height / 2), 
                           mouse_x - (screen_width / 2) );
    thats the rotation of the bitmap in radians. i didnt use graphics.h ( which i believe is the borland graphics library, correct me if im wrong ); mine was done in directx. but that one line of code was able to point the bitmap (which was always in the center of the screen) to the mouse pointer.
    I came up with a cool phrase to put down here, but i forgot it...

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