Diary During Summer Vacation 12

Continue with last week's work to add more editing features. Now the X, Y and Z axes can be selected by a left click and when it's seleted it becomes white to indicate its state. Then a drag & drop can move the control point towards the direction of the selected axis - demonstrated by Knot_Log12_0.png and Knot_Log12_1.png.

A feature to Add A New Internal Control Point Uing E key: To add a new control point between two existing control points on the string. Left click to select one control ball, holding on E key, continue to select next control ball using a left click. Two selected balls will become red. Then release the E key, press the E key again, a new control point will be added and a new control ball will be drawn at the position (Knot_Log12_2.png, Knot_Log12_3.png).

Another feature I have added on is to allow user to select an editing ball and then delete this control point. The operation of this one: Delete A Control Point Using D key: When the control balls are visible, a left click on a control ball will select this ball. The ball will become red and the X, Y, Z coordinators will appear on the ball. At this moment, press D key, this selected contorl point will be deleted (Knot_Log12_4.png).