//-------------------------------------------------------------------------
//fi_fire.c - fire tutorial source
//By Calvrak of Fusion Industries
//alexz@fusionindustries.com - http://www.fusionindustries.com
//You are free to modify this code and experiment with it.
//
//I'd be interested in any feedback or if this tutorial was of any
//  use to you.
//
//-Calvrak
//June 7, 1998
//
//This code was written and compiled under Microsoft Visual C v1.0
//It was tested under Borland C v3.0 and will compile under it if all the
//  _outp and _inp functions are changed to outp and inp.
//
//June 11, 1999
//*Code cleaned up. It's better, but not as good as I'd like.
//
//-------------------------------------------------------------------------

#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <malloc.h>

// P R O T O T Y P E S ------------------------------------------------------

void fire(void);
void Setpal(int col,unsigned char r,unsigned char g,unsigned char b);
void Create_Fire_Pal(void);
void Wait_For_Retrace(void);

// G L O B A L S ------------------------------------------------------------

unsigned char far *video_buffer = (char far *)0xA0000000L;
unsigned char far *double_buffer = NULL;

//---------------------------------------------------------------------------

void main()
{
    printf("Fire by Calvrak of Fusion Industries\n");
    printf("http://fusion.techcore.com\n");
    printf("\n\nPress any key to start the inferno!\n");
    getch();

    double_buffer = (unsigned char far *)_fmalloc(32000);

    //set video mode to VGA 320x200x256
    _asm
    {
        mov  ax, 13h
        int 10h
    }

    fire();

    _ffree(double_buffer);

    //set video mode back to text mode
    _asm
    {
        mov  ax, 03h
        int  10h
    }
}

//---------------------------------------------------------------------------

void fire(void)
{
    int x,y;    //screen coords
    int avg;    //average color
    int offset; //so we don't have to keep calc'ing 320*y+x all the time
    unsigned char color; //fire color


    //clear the double buffer
    _fmemset((unsigned char far *)double_buffer,0,64000);

    Create_Fire_Pal();

    while(!kbhit())
    {

        ////////////// S E E D ////////////////////////
        for(x=0; x<320; x++)
        {
            // bottom row(320*199+x) is white
            double_buffer[63680+x] = 255;
        }

        for(y=197; y<200; y++)
        {
            for(x=0; x<320; x+=8)
            {
                color = (char)rand()%256;     // get a random color
                offset = (y<<6) + (y<<8) + x; // calculate the offset

                if(color>128) color = 255; // all or nothing;
                if(color<127) color = 0;   // white or black

                // this just makes fatter fire -- horizontal 8-pixel
                // wide seed colors. Try changing this to just 4-pixel
                // wide seeds and see what happens.
                double_buffer[offset  ] = color;
                double_buffer[offset+1] = color;
                double_buffer[offset+2] = color;
                double_buffer[offset+3] = color;
                double_buffer[offset+4] = color;
                double_buffer[offset+5] = color;
                double_buffer[offset+6] = color;
                double_buffer[offset+7] = color;
            }
        }
        ////////// E N D  S E E D /////////////////////

        //////////////////// B L U R ///////////////////////////
        for(y=199; y>0; y--)
        {
            avg = 0;
            offset = (y<<6) + (y<<8); // 320 * y -- (calculate the next row)

            for(x=0; x<319; x++)
            {
                offset += 1; // equivalent to  320 * y + x + 1

                avg  = double_buffer[offset-320];//1    [x-320]      (1)
                avg += double_buffer[offset-1];  //2 [x-1][x][x+1] (2,3,4)
                avg += double_buffer[offset];    //3
                avg += double_buffer[offset+1];  //4

                avg = avg>>2;

                if(avg>1) avg -= 1; // make it fade faster
                                    // this also allows pixels with the
                                    // value of 1 to go to zero and
                                    // "extinguish". Try removing this line
                                    // to see what happens.


                // move "blurred" pixel up by one line
                double_buffer[offset - 320] = avg;
            }
        }
        ///////////////////////END BLUR/////////////////////

        Wait_For_Retrace(); // Don't want flicker ;)

        // copy everything except the seed rows to the video buffer (screen)
        _fmemcpy((char far *)video_buffer,
                 (char far *)double_buffer,
                 62720); // 62720 == 64000-4*320 for the seed rows
    }
}

//---------------------------------------------------------------------------

void Setpal(int col,unsigned char r,unsigned char g,unsigned char b)
{
    _outp(0x03C8,col);// 0x03C8 is write permission, col is the color number
    _outp(0x03C9,r);
    _outp(0x03C9,g);
    _outp(0x03C9,b);
}

//---------------------------------------------------------------------------

void Create_Fire_Pal()
{
    unsigned char i = 0;

    for (i=0; i<64; i++)
    {
        Setpal(    i,  i,    0, 0); // black to max red
        Setpal( i+64, 63,    i, 0); // max red to max yellow
        Setpal(i+128, 63,   63, 0); // max yellow
        Setpal(i+192, 63, 63-i, 0); // max yellow to red; we just do the
    }                               //  opposite of the color eqn above
}

//---------------------------------------------------------------------------

void Wait_For_Retrace(void)
{
    while(_inp(0x3DA) & 0x08);   // do nothing, retracing
    while(!(_inp(0x3DA) & 0x08));// wait for start of retrace
}