/// <summary>
/// Creates an <see cref="OrientedBoundingBox">OrientedBoundingBox</see> from a <see cref="BoundingBox">BoundingBox</see>.
/// </summary>
/// <param name="box">A <see cref="BoundingBox">BoundingBox</see> to create the <see cref="OrientedBoundingBox">OrientedBoundingBox</see> from</param>
/// <returns>The generated <see cref="OrientedBoundingBox">OrientedBoundingBox</see></returns>
public static OrientedBoundingBox FromAABB(BoundingBox box)
{
var center = BoundingVolumesExtensions.GetCenter(box);
var extents = BoundingVolumesExtensions.GetExtents(box);
return(new OrientedBoundingBox(center, extents));
}
/// <summary>
/// Calculates an OBB with a given set of points.
/// Tests every orientations between initValues and endValues, stepping through angle intervals with a given step size.
/// Goes on until it reaches a step less than 0.01
/// </summary>
/// <returns>A generated Oriented Bounding Box that contains the set of points</returns>
private static OrientedBoundingBox ComputeFromPointsRecursive(Vector3[] points, Vector3 initValues, Vector3 endValues,
float step)
{
var minObb = new OrientedBoundingBox();
var minimumVolume = float.MaxValue;
var minInitValues = Vector3.Zero;
var minEndValues = Vector3.Zero;
var transformedPoints = new Vector3[points.Length];
float y, z;
var x = initValues.X;
while (x <= endValues.X)
{
y = initValues.Y;
var rotationX = MathHelper.ToRadians(x);
while (y <= endValues.Y)
{
z = initValues.Z;
var rotationY = MathHelper.ToRadians(y);
while (z <= endValues.Z)
{
// Rotation matrix
var rotationZ = MathHelper.ToRadians(z);
var rotationMatrix = Matrix.CreateFromYawPitchRoll(rotationY, rotationX, rotationZ);
// Transform every point to OBB-Space
for (var index = 0; index < transformedPoints.Length; index++)
{
transformedPoints[index] = Vector3.Transform(points[index], rotationMatrix);
}
// Obtain an AABB enclosing every transformed point
var aabb = BoundingBox.CreateFromPoints(transformedPoints);
// Calculate the volume of the AABB
var volume = BoundingVolumesExtensions.GetVolume(aabb);
// Find lesser volume
if (volume < minimumVolume)
{
minimumVolume = volume;
minInitValues = new Vector3(x, y, z);
minEndValues = new Vector3(x + step, y + step, z + step);
// Restore the AABB center in World-Space
var center = BoundingVolumesExtensions.GetCenter(aabb);
center = Vector3.Transform(center, rotationMatrix);
// Create OBB
minObb = new OrientedBoundingBox(center, BoundingVolumesExtensions.GetExtents(aabb));
minObb.Orientation = rotationMatrix;
}
z += step;
}
y += step;
}
x += step;
}
// Loop again if the step is higher than a given acceptance threshold
if (step > 0.01f)
{
minObb = ComputeFromPointsRecursive(points, minInitValues, minEndValues, step / 10f);
}
return(minObb);
}