1, as shown in Figure A, the center stroke pen, after running smoothly for a period of time, gradually lifts the pen to make the lines gradually thinner, and finally leaves the paper. The pen is always vertical and the speed is constant. There are many choices for the length h of the linear gradual change section, such as 30 and 50. 80. 100 mm, etc.
2. As shown in Figure B, do the gradient exercise of the center line, with the pen vertical and even strokes. The selection of gradient segment length is the same as above.