void tileray::advance (int num)
{
last_dx = last_dy = 0;
int ax = abs(deltax);
int ay = abs(deltay);
int anum = abs (num);
for (int i = 0; i < anum; i++)
{
if (mostly_vertical ())
{ // mostly vertical line
leftover += ax;
if (leftover >= ay)
{
last_dx++;
leftover -= ay;
}
last_dy++;
}
else
{ // mostly horizontal line
leftover += ay;
if (leftover >= ax)
{
last_dy++;
leftover -= ax;
}
last_dx++;
}
steps++;
}
// offset calculated for 0-90 deg quadrant, we need to adjust if direction is other
int sx[4] = { 1, -1, -1, 1 };
int sy[4] = { 1, 1, -1, -1 };
int quadr = (direction / 90) % 4;
last_dx *= sx[quadr];
last_dy *= sy[quadr];
if (num < 0)
{
last_dx = -last_dx;
last_dy = -last_dy;
}
}
bool tileray::end ()
{
if (infinite)
return true;
return mostly_vertical()? steps >= abs(deltay) - 1 : steps >= abs(deltax) - 1;
}
int tileray::ortho_dy (int od)
{
int quadr = (direction / 90) % 4;
od *= sx[quadr];
return mostly_vertical()? 0 : od;
}
int tileray::ortho_dx (int od)
{
int quadr = (direction / 90) % 4;
od *= -sy[quadr];
return mostly_vertical()? od : 0;
}
int tileray::ortho_dy (int od)
{
return mostly_vertical()? 0 : od;
}
int tileray::ortho_dx (int od)
{
return mostly_vertical()? od : 0;
}