// bbox_intersect.ysl2

//

// bounding boxes intersection tests

// Rates 1D intersection of 2 segments A and B

// described respectively with a0,a1 and b0,b1

def "func:intersect_1d" {

// it is assumed that a1 > a0 and b1 > b0

param "a0";

param "a1";

param "b0";

param "b1";

const "d0", "$a0 >= $b0";

const "d1", "$a1 >= $b1";

choose {

when "not($d0) and $d1"

// b contained in a

// a0<b0 b1<a1

// a +--------+

// b +--+

result "3";

when "$d0 and not($d1)"

// a contained in b

// b0<a0 a1<b1

// a +--+

// b +--------+

result "2";

when "$d0 and $d1 and $a0 < $b1"

// a and b are overlapped

// b0<a0<b1<a1

// a +-----+

// b +-----+

result "1";

when "not($d0) and not($d1) and $b0 < $a1"

// a and b are overlapped

// a0<b0<a1<b1

// a +-----+

// b +-----+

result "1";

// since orientation doesn't matter,

// rated same as previous symetrical overlapping

otherwise

result "0"; /* no intersection*/

}

}

// Rates intersection A and B areas described with x,y,w and h

// attributes passed as $a and $b parameters.

//

// returns :

// 0 - no intersection

// .-----.

// .-----. | b|

// | | | |

// | | '-----'

// |a |

// '-----'

//

// 1 - overlapping

// .-----.

// .---|--. b|

// | | | |

// | '-----'

// |a |

// '------'

//

// 2 - overlapping

// .-----.

// | a |

// .---|-----|---.

// | '-----' |

// | b |

// '-------------'

//

// 3 - overlapping

// .-----.

// | b |

// .---|-----|---.

// | '-----' |

// | a |

// '-------------'

//

// 4 - a contained in b

// .-------------.

// | .-----. |

// | | a | |

// |b '-----' |

// '-------------'

//

// 6 - overlapping

// .----.

// | b|

// .---|----|---.

// |a | | |

// '---|----|---'

// '----'

//

// 9 - b contained in a

// .-------------.

// | .-----. |

// | | b | |

// |a '-----' |

// '-------------'

//

def "func:intersect" {

param "a";

param "b";

const "x_intersect", "func:intersect_1d($a/@x, $a/@x+$a/@w, $b/@x, $b/@x+$b/@w)";

choose{

when "$x_intersect != 0"{

const "y_intersect", "func:intersect_1d($a/@y, $a/@y+$a/@h, $b/@y, $b/@y+$b/@h)";

result "$x_intersect * $y_intersect";

}

otherwise result "0";

}

}