snakes.cpp

#include <sdl/SDL.h>
#include "video.h"
#include <math.h>

//
#define sint64   signed long long
#define uint32 unsigned int
#define sint32   signed int
#define uint16 unsigned short
#define sint16   signed short
#define uint8  unsigned char
#define sint8    signed char

//
const int c_ScreenWidth  = 640;
const int c_ScreenHeight = 480;

//
SDL_Surface *screen = NULL;

//
static inline void plot( int x, int y, int c )
{
    if ( x <  0              ) return;
    if ( y <  0              ) return;
    if ( x >= c_ScreenWidth  ) return;
    if ( y >= c_ScreenHeight ) return;
    Uint32 *p  = (Uint32*)screen->pixels;
            p += x + y * (screen->pitch >> 2);
           *p  = c;
}

//
bool start_sdl( void )
{
    //
    if ( SDL_Init( SDL_INIT_VIDEO ) != 0 )
        return false;
    //
    screen = SDL_SetVideoMode
    (
        c_ScreenWidth,
        c_ScreenHeight, 32, 0//SDL_FULLSCREEN
    );
    return ( screen != NULL );
}

//
const float pi = 3.14159265359f;

//
const int nodeCount = 27;

//
struct sTentacle
{
    float head;
    float girth;
    float friction;
    float muscleRange;
    float muscleFrequency;
    float tv;
    float theta;
    float count;
    float thetaMuscle;
    //
    float px;
    float py;
    //
    float x[ nodeCount ];
    float y[ nodeCount ];
};

//
float random( float range = 1.0f )
{
    float i  = (float)( rand( ) & 0xFFFF );
          i /= (float)   0xFFFF;
          i *= range;
    return i;
}

//
const int snakeCount = 7;
sTentacle snake[snakeCount];

//
void generate( sTentacle *t )
{
    t->count           = 0;
    t->theta           = 0;
    t->tv              = 0;
    t->thetaMuscle     = 0;
    t->head            =  2.0f + random( 4   );
    t->girth           =  8.0f + random( 12  );
    t->friction        =  0.9f + random( 10  ) / 100.0f;
    t->muscleRange     = 20.0f + random( 50  );
    t->muscleFrequency =  0.1f + random( 100 ) / 250.0f;
    //
    for ( int i=0; i<nodeCount; i++ )
    {
        t->x[i] = 0;
        t->y[i] = 0;
    }
    //
    t->px = -64;
    t->py = c_ScreenHeight/2 + random( 100 );
}

//
void update( sTentacle *t )
{
    //
    t->tv    += 0.5f * (random() - random( ));
    t->theta += t->tv;
    t->tv    *= t->friction;
    t->x[0]   = t->head * cos( pi / 180 * t->theta );
    t->y[0]   = t->head * sin( pi / 180 * t->theta );

    //
    t->count       += t->muscleFrequency;
    t->thetaMuscle  = t->muscleRange * sin( t->count );

    //
    t->x[1] = -t->head * cos( pi / 180 * ( t->theta + t->thetaMuscle ) );
    t->y[1] = -t->head * sin( pi / 180 * ( t->theta + t->thetaMuscle ) );

    //
    for ( int i=2; i<nodeCount; i++ )
    {
        float dx = t->x[i] - t->x[i-2];
        float dy = t->y[i] - t->y[i-2];

        //
        float  d = sqrtf( dx*dx + dy*dy );

        //
        t->x[i] = t->x[i-1] + (dx * t->girth) / d;
        t->y[i] = t->y[i-1] + (dy * t->girth) / d;

        //
        setColour( 0xFFFFFF );
        drawLine
        (
            t->px + (int)t->x[i  ],
            t->py + (int)t->y[i  ],
            t->px + (int)t->x[i-1],
            t->py + (int)t->y[i-1]
        );
    }

    drawCircle( t->px + t->x[0], t->py + t->y[0], 6 );

    t->px -= t->x[1];
    t->py -= t->y[1];

    //
    if ( t->px > c_ScreenWidth + 200 ) generate( t );

}

//
bool tick_sdl( void )
{
    SDL_Event event;
    while ( SDL_PollEvent( &event ) )
    {
        switch ( event.type )
        {
        case ( SDL_QUIT ):
            return false;
        case ( SDL_KEYDOWN ):
            if ( event.key.keysym.sym == SDLK_ESCAPE )
                return false;
            if ( event.key.keysym.sym == SDLK_r )
            {
                //
                for ( int i=0; i<snakeCount; i++ )
                    generate( &(snake[i]) );
            }
            break;
        }
    }
    return true;
}

//
int main( void )
{
    //
    if (! start_sdl  ( ) )  return -1;

    //
    for ( int i=0; i<snakeCount; i++ )
        generate( &(snake[i]) );

    //
    int time = SDL_GetTicks( );

    //
    while ( tick_sdl( ) )
    {
        //
        SDL_FillRect( screen, NULL, 0x000020 );


        //
        for ( int i=0; i<snakeCount; i++ )
            update( &(snake[i]) );

        //
        while ( true )
        {
            int dt = SDL_GetTicks( ) - time;
            if ( dt > 33 )
            {
                time += dt;
                break;
            }
            else
            {
                SDL_Delay( 1 );
            }
        }


        //
        SDL_Flip( screen );
    }
    //
    return 0;
}