/// <summary>Expands 'lhs' to include 'rhs'. Returns **rhs**</summary>
public static BBox Grow(ref BBox lhs, BBox rhs)
{
// Const version returns lhs, non-const returns rhs!
// Don't treat !rhs.IsValid as an error, it's the only way to grow an empty bbox
if (!rhs.IsValid)
{
return(rhs);
}
lhs = Union(lhs, rhs.Centre + rhs.Radius);
lhs = Union(lhs, rhs.Centre - rhs.Radius);
return(rhs);
}
/// <summary>
/// Clip a line segment to a bounding box returning the parametric values of the intersection.
/// Returns false if the line does not intersect with the bounding box.
/// Assumes initial values of 't0' and 't1' have been set.</summary>
public static bool Clip(BBox bbox, v4 point_, v4 direction_, ref float t0, ref float t1)
{
// Convert v4's to float arrays for efficient indexing
var lower = (float[])bbox.Lower();
var upper = (float[])bbox.Upper();
var point = (float[])point_;
var direction = (float[])direction_;
// For all three slabs
for (int i = 0; i != 3; ++i)
{
if (Math.Abs(direction[i]) < Math_.TinyF)
{
// Ray is parallel to slab. No hit if origin not within slab
if (point[i] < lower[i] || point[i] > upper[i])
{
return(false);
}
}
else
{
// Compute intersection t value of ray with near and far plane of slab
float u0 = (lower[i] - point[i]) / direction[i];
float u1 = (upper[i] - point[i]) / direction[i];
// Make u0 be intersection with near plane, u1 with far plane
if (u0 > u1)
{
Math_.Swap(ref u0, ref u1);
}
// Record the tightest bounds on the line segment
if (u0 > t0)
{
t0 = u0;
}
if (u1 < t1)
{
t1 = u1;
}
// Exit with no collision as soon as slab intersection becomes empty
if (t0 > t1)
{
return(false);
}
}
}
// Ray intersects all 3 slabs
return(true);
}
public static BBox operator *(m4x4 m, BBox rhs)
{
Debug.Assert(rhs.IsValid, "Transforming an invalid bounding box");
var bb = new BBox(m.pos, v4.Zero);
var mat = Math_.Transpose3x3(m);
bb.Centre.x += Math_.Dot(mat.x, rhs.Centre);
bb.Radius.x += Math_.Dot(Math_.Abs(mat.x), rhs.Radius);
bb.Centre.y += Math_.Dot(mat.y, rhs.Centre);
bb.Radius.y += Math_.Dot(Math_.Abs(mat.y), rhs.Radius);
bb.Centre.z += Math_.Dot(mat.z, rhs.Centre);
bb.Radius.z += Math_.Dot(Math_.Abs(mat.z), rhs.Radius);
return(bb);
}
/// <summary>Returns a bbox that encloses 'lhs' and 'rhs'</summary>
public static BBox Union(BBox lhs, BBox rhs)
{
// Const version returns lhs, non-const returns rhs!
// Don't treat !rhs.IsValid as an error, it's the only way to grow an empty bbox
var bb = lhs;
if (!rhs.IsValid)
{
return(bb);
}
bb = Union(bb, rhs.Centre + rhs.Radius);
bb = Union(bb, rhs.Centre - rhs.Radius);
return(bb);
}
/// <summary>Expands 'lhs' to include 'rhs'. Returns **rhs**</summary>
public static v4 Grow(ref BBox bbox, v4 point)
{
// Const version returns lhs, non-const returns rhs!
bbox = Union(bbox, point);
return(point);
}
