To solve the problem of acquiring the information of view outline

some experts have proposed many methods. But there are too much calculation and too complex determinant in prevail methods

which has become an important problem. Based on topological mapping

this paper puts forward automatically acquiring the information of view outline. At first

based on topological mapping principle

the method maps points of the candidate path onto the projection line. And then

using the topological sequence compatibility of points on the projection line and the candidate path

the problem of determining the trend of the next branch is converted to decision of the trend of projection lines. Finally

according to the sort order of mapping points

the path can be determined. Since the projection line is horizontal

it is easy and convenient to obtain the mapping points. This algorithm also saliently improves the computation efficiency by refraining from the complex angular calculations. Moreover

the algorithm will play an important role in automatic partitioning of engineering drawings

assembly diagram processing and dimension arrangement.