msdos asteroids

how do you make bullets?

metal casing filled with gunpowder

Code:

#define PI 3.14159
#define DEGTORAD(angle) (double)((angle)*(PI)/(180.0))

struct Bullet
{
  double x;
  double y;
  double speed;
  int angle;
};

void UpdateBullet(Bullet bt)
{
  bt.x+=(cos(DEGTORAD(bt.angle))*bt.speed);
  bt.y+=(sin(DEGTORAD(bt.angle))*bt.speed);
}

This is more suited to use in C++ through the use of classes. But this will work for plain C programming. It is not pretty since UpdateBullet and Bullet struct are really not logically grouped together.

class Bullet
{
double x;
double y;
int angle;
double speed;
public:
Bullet(void);
Update(void);
};

This class provides a much nicer way to deal with a bullet object and is more extensible and flexible (you can add more functions, data members, even derive off of this)

that looks right; thanks. now if i can just figure out how to apply it...to this...

Code:

#include <stdio.h>
#include <math.h>
#include <graphics.h>
#include <conio.h>
#include <dos.h>
#define rotate 3
#define speed 0.12

typedef struct
  {
   float x, y;
  } vec;

typedef struct
  {
   int num;
   vec array[3];
  } form;

typedef struct
  {
   vec   pixel;
   int   view;                               // ship direction.
   vec   move;                               // move direction.
   form  make;                               // make form.
   form  dos;                                // screen points.
  } image;

    image viper;

void array(vec*dest,vec*scr,int degree)      // return dest - points to x, y floats.
  {
   double rad;                               // radius.
   rad=degree*0.01745;
   dest->x=scr->x*cos(rad)-scr->y*sin(rad);  // standard library functions.
   dest->y=scr->x*sin(rad)+scr->y*cos(rad);
  }

void mode(image*var)                         // return value of type image.
  {
   int i;
   for(i=0;i<var->make.num;i++)              // rotate.
    {
     array(&var->dos.array[i],&var->make.array[i],var->view);
     var->dos.array[i].x+=var->pixel.x;
     var->dos.array[i].y+=var->pixel.y;
    }
  }

void draw(image*var)
  {
   int i;
   for(i=1;i<var->make.num;i++)
     {
      line(var->dos.array[i-1].x,var->dos.array[i-1].y,
	   var->dos.array[i].x,var->dos.array[i].y);
     }
   line(var->dos.array[i-1].x,var->dos.array[i-1].y,
	var->dos.array[0].x,var->dos.array[0].y);
  }

void power(image*var)
 {
  var->pixel.x+=var->move.x;var->pixel.y+=var->move.y;    // move.
  if(var->pixel.x<0)var->pixel.x=var->pixel.x+640;        // border.
  if(var->pixel.x>639)var->pixel.x=var->pixel.x-640;
  if(var->pixel.y<0)var->pixel.y=var->pixel.y+480;
  if(var->pixel.y>479)var->pixel.y=var->pixel.y-480;
 }

void hold(){while(inp(0x3da)&8);while(!(inp(0x3da)&8));}  // prevent flash.

void init(void)
  {
  int GraphicsDriver=VGA;
  int GraphicsMode=VGAHI;
  initgraph(&GraphicsDriver,&GraphicsMode,NULL);
  setwritemode(XOR_PUT);
  viper.make.num = 3;
  viper.make.array[ 0 ].x =  0; viper.make.array[ 0 ].y = -16;   // coords.
  viper.make.array[ 1 ].x = -8; viper.make.array[ 1 ].y =  +8;
  viper.make.array[ 2 ].x = +8; viper.make.array[ 2 ].y =  +8;
  viper.view = 0; viper.pixel.x = 320; viper.pixel.y = 240;      // center.
  viper.move.x = 0; viper.move.y = 0;
  }

void main(void)
  {
    int c=0; unsigned short keyboard;
    init();
    while(c!='q'&&c!='Q')
       {
	mode(&viper);draw(&viper);
	keyboard = *(unsigned short far *)MK_FP( 0x40, 0x17 );
	power(&viper);
	if(kbhit()){c=getch();}
	if(keyboard&0x0002)
	  {viper.view-=rotate;if(viper.view<0)viper.view=360-rotate;}
	if(keyboard&0x0001)
	  {viper.view+=rotate;if(viper.view>359)viper.view=0+rotate;}
	if(keyboard&0x0004)
	  {
	    // fire bullet.
	  }
	if(keyboard&0x0008)
	  {
	   double rad; rad = viper.view*0.01745;
	   viper.move.x+=sin(rad)*speed;viper.move.y-=cos(rad)*speed;
	  }
	hold();draw(&viper);

       }
   closegraph();
  }