Ray-AABB的十字路口

Question

所以，我需要做Ray-AABB交集这是我的代码，摘自一本书

    bool intersection(point start, point dir){
    float tmax, tmin, tmaxY, tminY, tmaxZ, tminZ;
    float a;
    point temp1, temp2;
    //check x
    a = 1 / dir[0];
    if(a > 0){
        tmax = (max[0] - start[0]) * a;
        tmin = (min[0] - start[0]) * a;
    }else{
        tmax = (min[0] - start[0]) * a;
        tmin = (max[0] - start[0]) * a;
    }
    if(tmin > tmax) return false;
    //check y
    a = 1 / dir[1];
    if(a > 0){
        tmaxY = (max[1] - start[1]) * a;
        tminY = (min[1] - start[1]) * a;
    }else{
        tmaxY = (min[1] - start[1]) * a;
        tminY = (max[1] - start[1]) * a;
    }
    if(tminY > tmin)    tmin = tminY;
    if(tmaxY < tmax)    tmax = tmaxY;
    if(tmin > tmax) return false;
    //check z
    a = 1 / dir[2];
    if(a > 0){
        tmaxZ = (max[2] - start[2]) * a;
        tminZ = (min[2] - start[2]) * a;
    }else{
        tmaxZ = (min[2] - start[2]) * a;
        tminZ = (max[2] - start[2]) * a;
    }
    if(tminZ > tmin)    tmin = tminZ;
    if(tmaxZ < tmax)    tmax = tmaxZ;
    if(tmin > tmax) return false;
    return true;
}

然而，它不适合我。上面的交集返回false(因为tminY> tmin但小于tmax)，而它应该返回true(测试时没有AABB边界)

观察:

    start(0, 0, 5) and dir(-89.5, -99.5, -100)
    bounding box: max(-5, 0, 0) and min(-5, -5, 0)
    tmin = 0.055865921
    tmax = 0.055865921
    tminY = 0
    tmaxY = 0.050251257, therefor tmax = 0.050251257
    Because tmin > tmax -> return false
    It is supposed to be true

如有任何帮助，不胜感激

Answer 1

// a degenerated bounding box, actually a segment parallel
//  with the yAxis, with a length of -5 and starting in (x,z)=(-5, 0)
// Because:
//    xMin=xMax=-5 - so a zero x extent
//    zMin=zMax=0  - so a zero x extent
bounding box: max(-5, 0, 0) and min(-5, -5, 0)

你确定那是你想要的吗?检查射线是否与线段相交?