To draw a curve, users can select command “Curve” in the Draw Menu or click the icon.
When command “Curve” selected, users can draw free curves by pressing the left button of the mouse and drag it.
When command “Curve” selected, users can move the mouse to the nodes on the middle of the curve and press the left button of the mouse to delete the current node.
When “Curve” commands selected, user can move the mouse to the node on the beginning of the curve and press the left button of the mouse to close the current curve automatically.
When command “Curve” selected, users can move the mouse to the node on the end of the curve and press the left button of the mouse to change the node of the current object into “sharp”.
When command “Curve” selected, users can move the mouse to the points which are not nodes and press the left button of the mouse to add a node to the current position of the curve.
