public Vector3 CalculateDrift(Vector3 position)
{
Vector3 drift = Math2.ProjectOnVector(Traits.Pivot, position) - Traits.Pivot;
if (drift.Length > 0.0001f)
{
Vector3 tangent = Vector3.Cross(drift, position);
tangent.Normalize();
float transverseDrift = Math2.Clamp(drift.Length * (float)Math.Tan(Traits.PivotRotation), -0.01f, .01f);
tangent *= transverseDrift;
return(tangent);
}
return(Vector3.Zero);
}
static Stress calculateStress(Vector3 movement0, Vector3 movement1, Vector3 boundaryVector, Vector3 boundaryNormal)
{
var relativeMovement = movement0 - movement1;
var pressureVector = Math2.ProjectOnVector(relativeMovement, boundaryNormal);
var pressure = pressureVector.Length;
if (Vector3.Dot(pressureVector, boundaryNormal) > 0)
{
pressure = -pressure;
}
var shear = Math2.ProjectOnVector(relativeMovement, boundaryVector).Length;
return(new Stress(2.0f / (1.0f + (float)Math.Exp(-pressure / 30.0f)) - 1.0f,
2.0f / (1.0f + (float)Math.Exp(-shear / 30.0f)) - 1.0f));
}
public Vector3 CalculateSpin(Vector3 position)
{
// Combine transverse movement about center and pivot.
// First project center onto position vector to get an orthogonal spin vector.
Vector3 spin = Math2.ProjectOnVector(Traits.Center, position) - Traits.Center;
if (spin.Length > 0.0001f)
{
Vector3 tangent = Vector3.Cross(spin, position);
tangent.Normalize();
tangent *= spin.Length * (float)Math.Tan(Traits.CenterRotation);
return(tangent);
}
return(Vector3.Zero);
}