void AxisIntersect(float min, float max, float p, float d, float& tfirst, float& tlast){    if (fabs(d) > 1.0E-8f)    {        float t0 = (min - p) / d;        float t1 = (max - p) / d;        if (t0 > t1) swap(t0, t1);        if (t0 > tfirst) tfirst = t0;        if (t1 < tlast)  tlast = t1;        if (tmast < tfirst) return false;        retrun true;    }    else    {        return (p > min) && (p < max);    }}bool BoxRayIntersect(Vector Min, Vector Max, Vector P, Vector D, float maxt){    float mint = 0;    if (!AxisIntersect(Min.x, Max.x, P.x, D.x, mint, maxt))         return false;    if (!AxisIntersect(Min.y, Max.y, P.y, D.y, mint, maxt))         return false;    if (!AxisIntersect(Min.z, Max.z, P.z, D.z, mint, maxt))         return false;    return true;}

/*  missed intersection.  --------------------  intervals [tymin, tymax] and [txmin, txmax] do not overlap (here, txmin > tymax)                  |     |                 |     |        *P0      |     |         \       |     |          \tymin |     |   --------*-----+-----+-----------------            \    |     |             \   |     |   -----------*--+-----+-----------------         tymax \ |     |                 \|     |                  *txmin|                  |\    |                  | \   |                  |  \  |                  |   \ |                  |    \|                  |     *txmax                  |     |\                  |     | \                  |     |  *P1   we have  intersection.  ----------------------  intervals [tymin, tymax] and [txmin, txmax] overlap (tymin < txmax and tymax > txmin)           *P0 |      |            \  |      |             \ |      |              \|txmin |               *      |               |\ tymin --------------+-*----+-----------------               |  \   |               |   \ tymax --------------+----*-+-----------------               |     \|               |      *txmax                |      |\                |      | \                 |      |  \                    |      |   *P1                |      | in code, you start off with a ray where tfirst = 0.0f, and tlast = |P1 - P0|- first, you test intersection with the two X planes=> will give you [txmin, txmax]=> also, you notice that txmin > tfirst, and txmax < tlast, so then    tfirst = txmin, tlast = txmax- second, you test with the Y planes=> will give you [tymin, tymax]=> here also, (tymin > tfirst), so tfirst = tymin=>            (tymax < tlast),  so tlast  = tymax- finally, (tlast > tfirst). this is consistent. so we have an intersection.in case of no intersection-------------------------- first, you test intersection with the two X planes=> will give you [txmin, txmax]=> also, you notice that txmin > tfirst, and txmax < tlast, so then    tfirst = txmin, tlast = txmax- second, you test with the Y planes=> will give you [tymin, tymax]=> but here, tymin is not > tfirst=>            (tymax < tlast),  so tlast  = tymax- finally, now that we have tfirst = txmin, tlast = tymaxbut, (tfirst > tlast). discrepency, the interseciton is invalid.- bottom line-------------you keep testing intersections with pairs of planes along axes. -> you keep reducing the initial interval [tfirst, tlast] with the small values   for both. -> As soon as the interval becomes invalidated, it means that the ray missed the box and there   is no intersection./**/

bool CRasteriser::ClipSegment(float min, float max, float a, float b, float d, float& t0, float& t1){	const float threshold = 1.0e-6f;	if (Abs(d) < threshold)	{		if (d > 0.0f)		{			return !(b < min || a > max);		}		else		{			return !(a < min || b > max);		}	}	float u0, u1;	u0 = (min - a) / (d);	u1 = (max - a) / (d);	if (u0 > u1) 	{		Swap(u0, u1);	}	if (u1 < t0 || u0 > t1)	{		return false;	}	t0 = Max(u0, t0);	t1 = Min(u1, t1);	if (t1 < t0)	{		return false;	}	return true; }bool CRasteriser::ClipSegment(Vector& A, Vector& B, const Vector& Min, const Vector& Max){	Vector S = A;	Vector D = (B - A);	float t0 = 0.0f, t1 = 1.0f;	if (!ClipSegment(Min.x, Max.x, A.x, B.x, D.x, t0, t1)) 	{		return false;	}		if (!ClipSegment(Min.y, Max.y, A.y, B.y, D.y, t0, t1)) 	{		return false;	}	if (!ClipSegment(Min.z, Max.z, A.z, B.z, D.z, t0, t1)) 	{		return false;	}	A = S + D * t0;	B = S + D * t1;	return true;}