public override Matrix4?GetTransformationMatrix(Viewport2D viewport, ViewportEvent e, BaseBoxTool.BoxState state, Document doc, IEnumerable <Widget> activeWidgets)
{
var origin = viewport.ZeroUnusedCoordinate((state.PreTransformBoxStart + state.PreTransformBoxEnd) / 2);
var rw = activeWidgets.OfType <RotationWidget>().FirstOrDefault();
if (rw != null)
{
origin = rw.GetPivotPoint();
}
var forigin = viewport.Flatten(origin);
var origv = (state.MoveStart - forigin).Normalise();
var newv = (viewport.ScreenToWorld(e.X, viewport.Height - e.Y) - forigin).Normalise();
var angle = DMath.Acos(Math.Max(-1, Math.Min(1, origv.Dot(newv))));
if ((origv.Cross(newv).Z < 0))
{
angle = 2 * DMath.PI - angle;
}
var shf = KeyboardState.Shift;
var def = Select.RotationStyle;
var snap = (def == RotationStyle.SnapOnShift && shf) || (def == RotationStyle.SnapOffShift && !shf);
if (snap)
{
var deg = angle * (180 / DMath.PI);
var rnd = Math.Round(deg / 15) * 15;
angle = rnd * (DMath.PI / 180);
}
Matrix4 rotm;
if (viewport.Direction == Viewport2D.ViewDirection.Top)
{
rotm = Matrix4.CreateRotationZ((float)angle);
}
else if (viewport.Direction == Viewport2D.ViewDirection.Front)
{
rotm = Matrix4.CreateRotationX((float)angle);
}
else
{
rotm = Matrix4.CreateRotationY((float)-angle); // The Y axis rotation goes in the reverse direction for whatever reason
}
var mov = Matrix4.CreateTranslation((float)-origin.X, (float)-origin.Y, (float)-origin.Z);
var rot = Matrix4.Mult(mov, rotm);
return(Matrix4.Mult(rot, Matrix4.Invert(mov)));
}