Model simplification is very important in the fields of virtual reality and real-time simulation. In computer graphics

objects and scenes are often described by mesh models

such as terrain model

Stanford's scanning models and so on

but

a complicated model often includes large-scale data

the large data scale is a bottle-neck of fast-speed rendering

so it is necessary to simplify mesh model. The approach of levels of detail(LOD) is good

there have been some efficient algorithms for LOD and model simplification

these algorithms' simplification criteria are minimizing the geometry errors. It has been found that the last destination for simplification is to obtain fast rendering speed as well as good visual effects

hence

visual effects can and should become simplification criteria. This paper gives an algorithm of normal-based mesh model simplification. First

this paper gives a mathematics model for curve

and concludes that grads can express a curve's visual effects. Second

this paper uses normal of mesh models to replace grads

if the normal is averaged three times or more

a mesh can simulate a cure well

and the averaged normal can replace grads to become simplification criteria. Finally

this paper defines an angle between a normal of given point of intersection of the mesh model and those around this point

and uses this angle to simply mesh models. A group of experimental results are also given

which illustrate that the above algorithm can realize model simplification effectively

and at the same time

keep the models highly accurate.