Polygon modeling

Learning tasks:
Mainly know the polygon editing tool commands, use the polygon editing commands to build the models, and flexibly use various editing tools to make more models. Lay the foundation for the next scenes making.

Notes：
1. Polygon modeling: points, lines and areas
2. Close polygonal holes (add polygons to form a complete picture)
3. Polygonal brush
4. Create Point Tool
5. Brush (similar to liquefaction function)
6. Slide (when moving points and lines, it can move along the side of the object)
7. Stitching and welding: Stitching and welding tools are very similar, they are all connection points, lines, and surfaces. The difference is that the soldered connection point is in the middle.
8. Chamfer: Turn right-angled edges into rounded corners
9. Squeeze: highlight the surface or line, you can choose to keep the group
10. Split tool and disconnect: Disconnect is to disconnect the current face from it, split is to separate into a face, and there is an additional split object in the object bar