int FollowTrace (fixed tracex, fixed tracey, long deltax, long deltay, int max)
{
int tx,ty,otx,oty;
long absdx,absdy,xstep,ystep;
tx = tracex>>TILESHIFT;
ty = tracey>>TILESHIFT;
absdx=LABS(deltax);
absdy=LABS(deltay);
if (absdx>absdy)
{
ystep = (deltay<<8)/(absdx>>8);
if (!ystep)
ystep = deltay>0 ? 1 : -1;
oty = (tracey+ystep)>>TILESHIFT;
if (deltax>0)
{
//###############
//
// step x by +1
//
//###############
do
{
tx++;
tracey+=ystep;
ty = tracey>>TILESHIFT;
if (ty!=oty)
{
if (tilemap[tx-1][ty])
{
tile.x = tx-1;
tile.y = ty;
return 1;
}
oty = ty;
}
if (tilemap[tx][ty])
{
tile.x = tx;
tile.y = ty;
return 1;
}
} while (--max);
return 0;
}
else
{
//###############
//
// step x by -1
//
//###############
do
{
DVECTOR xdvinit(double j, double incr, double n)
{
long k;
long num;
DVECTOR x;
if ((incr > 0.0 && j > n) || (incr < 0.0 && j < n)) {
x = xdvnull();
return x;
}
if (incr == 0.0) {
num = (long)n;
if (num <= 0) {
x = xdvnull();
return x;
}
} else {
num = LABS((long)((n - j) / incr)) + 1;
}
/* memory allocate */
x = xdvalloc(num);
/* initailize data */
for (k = 0; k < x->length; k++) {
x->data[k] = j + (k * incr);
}
return x;
}