public void SetATA(ref Matrix3d A)
{
Vector3d c0 = A.Column(0), c1 = A.Column(1), c2 = A.Column(2);
entries[0] = c0.LengthSquared;
entries[1] = c1.LengthSquared;
entries[2] = c2.LengthSquared;
entries[3] = c0.Dot(c1);
entries[4] = c0.Dot(c2);
entries[5] = c1.Dot(c2);
}
// ported from WildMagic5 Wm5ContBox3.cpp::MergeBoxes
public static Box3d Merge(ref Box3d box0, ref Box3d box1)
{
// Construct a box that contains the input boxes.
var box = new Box3d();
// The first guess at the box center. This value will be updated later
// after the input box vertices are projected onto axes determined by an
// average of box axes.
box.Center = 0.5 * (box0.Center + box1.Center);
// A box's axes, when viewed as the columns of a matrix, form a rotation
// matrix. The input box axes are converted to quaternions. The average
// quaternion is computed, then normalized to unit length. The result is
// the slerp of the two input quaternions with t-value of 1/2. The result
// is converted back to a rotation matrix and its columns are selected as
// the merged box axes.
Quaterniond q0 = new Quaterniond(), q1 = new Quaterniond();
var rot0 = new Matrix3d(ref box0.AxisX, ref box0.AxisY, ref box0.AxisZ, false);
q0.SetFromRotationMatrix(ref rot0);
var rot1 = new Matrix3d(ref box1.AxisX, ref box1.AxisY, ref box1.AxisZ, false);
q1.SetFromRotationMatrix(ref rot1);
if (q0.Dot(q1) < 0)
{
q1 = -q1;
}
Quaterniond q = q0 + q1;
double invLength = 1.0 / Math.Sqrt(q.Dot(q));
q = q * invLength;
Matrix3d q_mat = q.ToRotationMatrix();
box.AxisX = q_mat.Column(0); box.AxisY = q_mat.Column(1); box.AxisZ = q_mat.Column(2); //q.ToRotationMatrix(box.Axis);
// Project the input box vertices onto the merged-box axes. Each axis
// D[i] containing the current center C has a minimum projected value
// min[i] and a maximum projected value max[i]. The corresponding end
// points on the axes are C+min[i]*D[i] and C+max[i]*D[i]. The point C
// is not necessarily the midpoint for any of the intervals. The actual
// box center will be adjusted from C to a point C' that is the midpoint
// of each interval,
// C' = C + sum_{i=0}^2 0.5*(min[i]+max[i])*D[i]
// The box extents are
// e[i] = 0.5*(max[i]-min[i])
int i, j;
double dot;
var vertex = new Vector3d[8];
Vector3d pmin = Vector3d.Zero;
Vector3d pmax = Vector3d.Zero;
box0.ComputeVertices(vertex);
for (i = 0; i < 8; ++i)
{
Vector3d diff = vertex[i] - box.Center;
for (j = 0; j < 3; ++j)
{
dot = box.Axis(j).Dot(ref diff);
if (dot > pmax[j])
{
pmax[j] = dot;
}
else if (dot < pmin[j])
{
pmin[j] = dot;
}
}
}
box1.ComputeVertices(vertex);
for (i = 0; i < 8; ++i)
{
Vector3d diff = vertex[i] - box.Center;
for (j = 0; j < 3; ++j)
{
dot = box.Axis(j).Dot(ref diff);
if (dot > pmax[j])
{
pmax[j] = dot;
}
else if (dot < pmin[j])
{
pmin[j] = dot;
}
}
}
// [min,max] is the axis-aligned box in the coordinate system of the
// merged box axes. Update the current box center to be the center of
// the new box. Compute the extents based on the new center.
for (j = 0; j < 3; ++j)
{
box.Center += (0.5 * (pmax[j] + pmin[j])) * box.Axis(j);
box.Extent[j] = 0.5 * (pmax[j] - pmin[j]);
}
return(box);
}
