Original Post
I have an OBB class that has the following: I can then derive the world transform for the OBB as the following: and the 1D test for intersection for each separating axis should also be correct, as it works for other shapes: I've stepped through the code and the problem is that the mtv_Distance is too small a value, which doesn't resolve the OBB penetration. Can anyone point out any glaring errors in my code so far, it would really help me as I can't understand why this is happening. Thank you.
Vector3[] axes; // Local x, y and z axes
Vector3 extents; // Positive halfwidth extents of the OBB along each axis
Quaternion orientation = Quaternion.Identity; // Orientation of OBB (Rotation matrix is derived from this)
Vector3 position;
Matrix rotation;
public void UpdateRotation(float yaw, float pitch, float roll)
{
if (yaw == 0f && pitch == 0f && roll == 0f)
{
return;
}
Quaternion rotation_Additional = Quaternion.CreateFromYawPitchRoll(yaw, pitch, roll);
orientation *= rotation_Additional;
orientation.Normalize();
rotation = Matrix.CreateFromQuaternion(orientation);
// Local X, Y and Z axes
axes[0] = rotation.Right;
axes[1] = rotation.Up;
axes[2] = rotation.Forward;
recreateWorld = true;
}
world_Transform =
Matrix.CreateScale(extents * 2f) *
rotation *
Matrix.CreateTranslation(position);
public void CalculateSlab(Vector3 axis, ref float min, ref float max)
{
// • A slab is the infinite region of space between two planes
// • The min and max values are then the required scalar values defining the plane positions
float pos = Vector3.Dot(position, axis);
float ext =
Math.Abs(Vector3.Dot(axes[0], axis)) * extents.X +
Math.Abs(Vector3.Dot(axes[1], axis)) * extents.Y +
Math.Abs(Vector3.Dot(axes[2], axis)) * extents.Z;
min = pos - ext;
max = pos + ext;
}
private static bool IntersectThruAxis(Vector3 axis, CD_AABB a, CD_OBB b, ref float mtv_Distance, ref Vector3 mtv_Axis)
{
// [Separating Axis Theorem]
// • Two convex shapes only overlap if they overlap on all axes of separation
// • In order to create accurate responses we need to find the collision vector (Minimum Translation Vector)
// • Find if the two boxes intersect along a single axis
// • Compute the intersection interval for that axis
// • Keep the smallest intersection/penetration value
float a_Min = float.MaxValue;
float a_Max = float.MinValue;
float b_Min = float.MaxValue;
float b_Max = float.MinValue;
a.CalculateSlab(axis, ref a_Min, ref a_Max);
b.CalculateSlab(axis, ref b_Min, ref b_Max);
// Find distance intervals for current two slabs
// Distance is between slab min/max values
float d_S0 = a_Min - b_Max;
float d_S1 = b_Min - a_Max;
// The distance is positive if the intervals do not overlap
// Must be >= to 0 and not > 0, otherwise MTV can equal Vector3.Zero and cause NaN
if (d_S0 >= 0f || d_S1 >= 0f)
{
return false;
}
// Current distance interval for slabs [A_Min, A_Max] and [B_Min, B_Max]
float d = (d_S0 > d_S1) ? -d_S0 : d_S1;
// If d is the smallest distance so far
if (Math.Abs(d) < Math.Abs(mtv_Distance))
{
// Store the distance and the current axis
mtv_Distance = d;
mtv_Axis = axis;
}
return true;
}