static bool line_line_intersection(vec2 a0, vec2 a1, vec2 b0, vec2 b1)
{
#if 1
// Implemented based on http://stackoverflow.com/a/17198094/4354008
vec2 v = vec2_sub(a0, a1);
vec2 normal = vec2_new(v.y, -v.x);
vec2 v0 = vec2_sub(b0, a0);
vec2 v1 = vec2_sub(b1, a0);
float proj0 = vec2_dot(v0, normal);
float proj1 = vec2_dot(v1, normal);
if ((proj0 == 0) || (proj1 == 0))
return true;
// TODO: float_sign()
if ((proj0 > 0) && (proj1 < 0))
return true;
if ((proj0 < 0) && (proj1 > 0))
return true;
return false;
#else
vec2 intersection = vec2_zero();
vec2 b = vec2_sub(a1, a0);
vec2 d = vec2_sub(b1, b0);
float b_dot_p_perp = (b.x * d.y) - (b.y * d.x);
if (b_dot_p_perp == 0)
return false;
vec2 c = vec2_sub(b0, a0);
float t = ((c.x * d.y) - (c.y * d.x)) / b_dot_p_perp;
if ((t < 0) || (t > 1))
return false;
float u = ((c.x * b.y) - (c.y * b.x)) / b_dot_p_perp;
if ((u < 0) || (u > 1))
return false;
// TODO: make this an output parameter
intersection = vec2_add(a0, vec2_mul(b, t));
return true;
#endif
}
static float get_angle(const float a0[2], const float a1[2],
const float b0[2], const float b1[2])
{
float u[2], v[2], dot, det;
vec2_sub(a1, a0, u);
vec2_normalize(u, u);
vec2_sub(b1, b0, v);
vec2_normalize(v, v);
dot = vec2_dot(u, v);
det = vec2_cross(u, v);
return atan2(det, dot);
}
/////////////////////////////
// Input_GetDir
//
// Reports the direction of the dpad.
int Input_GetDir(vec2 dir) {
float vlen;
Uint8 buttons;
int mx, my;
float dlen;
extern int _width, _height;
// Get mouse state
buttons = SDL_GetMouseState(&mx, &my);
if (buttons) {
// Use the mouse
vec2_set(dir, mx - (_width / 2), my - (_height / 2.0f));
dlen = 1.0f / sqrtf(vec2_dot(dir, dir));
vec2_scale(dir, dir, dlen);
return (1);
} else {
// Use the keyboar
vec2_set(dir, 0.0f, 0.0f);
if (Input_GetKey(InputKey_Up)) {
dir[1] -= 1.0f;
}
if (Input_GetKey(InputKey_Down)) {
dir[1] += 1.0f;
}
if (Input_GetKey(InputKey_Left)) {
dir[0] -= 1.0f;
}
if (Input_GetKey(InputKey_Right)) {
dir[0] += 1.0f;
}
vlen = vec2_dot(dir, dir);
if (vlen > 0.0f) {
vlen = sqrtf(vlen);
vec2_scale(dir, dir, 1.0f / vlen);
return (1);
} else {
return (0);
}
}
}
static int _llfunc_vec2_dot(lua_State *L) {
vec2 *a = (vec2*)userdata_get_or_die(L, 1);
vec2 *b = (vec2*)userdata_get_or_die(L, 2);
lua_pushnumber(L, vec2_dot(a, b));
return 1;
}