Among the graphical tools, there is a tool called "curve". It is a tool that draws a straight line by the first drag, and an arc is drawn between the two ends that was initially determined by the second drag. It is useful to use something together with a perspective ruler.

It is very easy to draw a little troubled part such as architectural structure where depth and arc combine, such as arches with handrails and windows, and curved parts of furniture. Continuous arches are beautiful if you display a perspective grid and draw an arc with a square as a guide.

It is also useful for drawing other cutlery such as long-curved Japanese swords.