4-Ever Doomed/4-everdoomedcypresssoftware1994.iso/utils/d1/bsp_os2/picknode.c

C/C++ Source or Header | 1994-04-14 | 7KB | 195 lines

/*- PICKNODE.C --------------------------------------------------------------*
 To be able to divide the nodes down, this routine must decide which is the
 best Seg to use as a nodeline. It does this by selecting the line with least
 splits and has least difference of Segs on either side of it.

 Credit to Raphael Quinet and DEU, this routine is a copy of the nodeline
 picker used in DEU5beta. I am using this method because the method I
 originally used was not so good.
*---------------------------------------------------------------------------*/

struct Seg *PickNode(struct Seg *ts)
{
    int num_splits,num_left,num_right;
    int min_splits,min_diff,val;
    struct Seg *part,*check,*best;
    int max,new,grade = 0,bestgrade = 32767,seg_count;

   min_splits = 32767;
   min_diff = 32767;
   best = ts;                                    /* Set best to first (failsafe measure)*/

    for(part=ts;part;part = part->next)    /* Use each Seg as partition*/
        {
        progress();                                /* Something for the user to look at.*/

        psx = vertices[part->start].x;    /* Calculate this here, cos it doesn't*/
        psy = vertices[part->start].y;    /* change for all the interations of*/
        pex = vertices[part->end].x;        /* the inner loop!*/
        pey = vertices[part->end].y;
        pdx = psx - pex;                        /* Partition line DX,DY*/
        pdy = psy - pey;

        num_splits = 0;
        num_left = 0;
        num_right = 0;

        seg_count = 0;
        for(check=ts;check;check=check->next)    /* Check partition against all Segs*/
            {
            seg_count++;
            if(check == part) num_right++;        /* If same as partition, inc right count*/
            else
                {
                lsx = vertices[check->start].x;    /* Calculate this here, cos it doesn't*/
                lsy = vertices[check->start].y;    /* change for all the interations of*/
                lex = vertices[check->end].x;        /* the inner loop!*/
                ley = vertices[check->end].y;
                val = DoLinesIntersect();            /* get state of lines relation to each other*/
                if((val&2 && val&64) || (val&4 && val&32))
                    {
                    num_splits++;                        /* If line is split, inc splits*/
                    num_left++;                            /* and add one line into both*/
                    num_right++;                        /* sides*/
                    }
                else
                    {
                    if(val&1 && val&16)                /* If line is totally in same*/
                        {                                    /* direction*/
                        if(check->flip == part->flip) num_right++;
                        else num_left++;                /* add to side according to flip*/
                        }
                    else                                    /* So, now decide which side*/
                        {                                    /* the line is on*/
                        if(val&34) num_left++;        /* and inc the appropriate*/
                        if(val&68) num_right++;        /* count*/
                        }
                    }
                }
/*            if(num_splits > min_splits) break;    /* If more splits than last, reject*/
            }

        if(num_right > 0 && num_left > 0)        /* Make sure at least one Seg is*/
            {                                                /* on either side of the partition*/
            max = max(num_right,num_left);
            new = (num_right + num_left) - seg_count;
            grade = max+new*8;

            if(grade < bestgrade)
                {
                bestgrade = grade;
                best = part;                            /* and remember which Seg*/
                }
            }
        }
    return best;                                        /* all finished, return best Seg*/
}

/*---------------------------------------------------------------------------*
 Because this is used a horrendous amount of times in the inner loops, the
 coordinate of the lines are setup outside of the routine in global variables
 psx,psy,pex,pey = partition line coordinates
 lsx,lsy,lex,ley = checking line coordinates
 The routine returns 'val' which has 3 bits assigned to the the start and 3
 to the end. These allow a decent evaluation of the lines state.
 bit 0,1,2 = checking lines starting point and bits 4,5,6 = end point
 these bits mean     0,4 = point is on the same line
                         1,5 = point is to the left of the line
                        2,6 = point is to the right of the line
 There are some failsafes in here, these mainly check for small errors in the
 side checker.
*---------------------------------------------------------------------------*/

int DoLinesIntersect()
{
    short int x,y,val = 0;

    long dx2,dy2,dx3,dy3,a,b,l;

    dx2 = psx - lsx;                                    /* Checking line -> partition*/
    dy2 = psy - lsy;
    dx3 = psx - lex;
    dy3 = psy - ley;

    a = pdy*dx2 - pdx*dy2;
    b = pdy*dx3 - pdx*dy3;

    if((a<0 && b>0) || (a>0 && b<0))                /* Line is split, just check that*/
        {
        ComputeIntersection(&x,&y);
        dx2 = lsx - x;                                    /* Find distance from line start*/
        dy2 = lsy - y;                                    /* to split point*/
        if(dx2 == 0 && dy2 == 0) a = 0;
        else
            {
            l = (long)sqrt((float)((dx2*dx2)+(dy2*dy2)));        /* If either ends of the split*/
            if(l < 2) a = 0;                            /* are smaller than 2 pixs then*/
            }                                                /* assume this starts on part line*/
        dx3 = lex - x;                                    /* Find distance from line end*/
        dy3 = ley - y;                                    /* to split point*/
        if(dx3 == 0 && dy3 == 0) b = 0;
        else
            {
            l = (long)sqrt((float)((dx3*dx3)+(dy3*dy3)));        /* same as start of line*/
            if(l < 2) b = 0;
            }
        }

    if(a == 0) val = val | 16;                        /* start is on middle*/
    if(a < 0) val = val | 32;                        /* start is on left side*/
    if(a > 0) val = val | 64;                        /* start is on right side*/

    if(b == 0) val = val | 1;                        /* end is on middle*/
    if(b < 0) val = val | 2;                        /* end is on left side*/
    if(b > 0) val = val | 4;                        /* end is on right side*/

    return val;
}

/*---------------------------------------------------------------------------*
 Calculate the point of intersection of two lines. ps?->pe? & ls?->le?
 returns int xcoord, int ycoord
*---------------------------------------------------------------------------*/

void ComputeIntersection(short int *outx,short int *outy)
{
    double a,b,a2,b2,l,l2,w,d,z;

    long dx,dy,dx2,dy2;

    dx = pex - psx;
    dy = pey - psy;
    dx2 = lex - lsx;
    dy2 = ley - lsy;

    if(dx == 0 && dy == 0) ProgError("Trouble in ComputeIntersection dx,dy");
    l = (long)sqrt((float)((dx*dx) + (dy*dy)));
    if(dx2 == 0 && dy2 == 0) ProgError("Trouble in ComputeIntersection dx2,dy2");
    l2 = (long)sqrt((float)((dx2*dx2) + (dy2*dy2)));

    a = dx / l;
    b = dy / l;
    a2 = dx2 / l2;
    b2 = dy2 / l2;
    d = b * a2 - a * b2;
    w = lsx;
    z = lsy;
    if(d != 0.0)
        {
        w = (((a*(lsy-psy))+(b*(psx-lsx))) / d);

/*        printf("Intersection at (%f,%f)\n",x2+(a2*w),y2+(b2*w));*/

        a = lsx+(a2*w);
        b = lsy+(b2*w);
        modf((float)(a)+ ((a<0)?-0.5:0.5) ,&w);
        modf((float)(b)+ ((b<0)?-0.5:0.5) ,&z);
        }

    *outx = w;
    *outy = z;
}

/*--------------------------------------------------------------------------*/