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/*
* File: ray.cc
* Summary: Diamond grid wrapper around geom::ray.
*
* The geom::grid diamonds is a checkerboard grid rotated
* by 45 degrees such that the black cells ("diamonds") lie just
* within the normal crawl map cells.
*
* ray_def provides for advancing and reflecting rays in
* map coordinates, where a ray touches a given cell if it
* meets the diamond.
*/
#include "AppHdr.h"
#include <cmath>
#include "los.h"
#include "ray.h"
#include "geom2d.h"
static geom::grid diamonds(geom::lineseq(1, 1, 0.5, 1),
geom::lineseq(1, -1, -0.5, 1));
static int ifloor(double d)
{
return static_cast<int>(floor(d));
}
static bool double_is_integral(double d)
{
return (double_is_zero(d - round(d)));
}
// Is v in a diamond?
static bool in_diamond(const geom::vector &v)
{
int i1 = ifloor(diamonds.ls1.index(v));
int i2 = ifloor(diamonds.ls2.index(v));
return ((i1 + i2) % 2 == 0);
}
// Is v in the interiour of a diamond?
static bool in_diamond_int(const geom::vector &v)
{
double d1 = diamonds.ls1.index(v);
double d2 = diamonds.ls2.index(v);
return (!double_is_integral(d1) && !double_is_integral(d2));
}
// Is v an intersection of grid lines?
static bool is_corner(const geom::vector &v)
{
double d1 = diamonds.ls1.index(v);
double d2 = diamonds.ls2.index(v);
return (double_is_integral(d1) && double_is_integral(d2));
}
coord_def ray_def::pos() const
{
// XXX: pretty arbitrary if we're just on a corner.
int x = ifloor(r.start.x);
int y = ifloor(r.start.y);
return (coord_def(x, y));
}
// Return false if we passed or hit a corner.
bool ray_def::advance()
{
ASSERT(on_corner || in_diamond_int(r.start));
if (on_corner)
{
ASSERT (is_corner(r.start));
on_corner = false;
r.move_half_cell(diamonds);
}
else
{
// Starting inside a diamond.
bool c = !r.to_next_cell(diamonds);
if (c)
{
// r is now on a corner, going from diamond to diamond.
r.move_half_cell(diamonds);
return (false);
}
}
// Now inside a non-diamond.
ASSERT(!in_diamond(r.start));
if (r.to_next_cell(diamonds))
{
ASSERT(in_diamond_int(r.start));
return (true);
}
else
{
// r is now on a corner, going from non-diamond to non-diamond.
ASSERT(is_corner(r.start));
on_corner = true;
return (false);
}
}
void ray_def::bounce(const reflect_grid &rg)
{
ASSERT(in_diamond(r.start));
// Find out which side of the diamond r leaves through.
geom::ray copy = r;
r.dir = -r.dir;
}
void ray_def::regress()
{
r.dir = -r.dir;
advance();
r.dir = -r.dir;
}
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