Common methods for describing 3D models of objects and their advantages and disadvantages

A three-dimensional model of an object

• Wireframe model
• Surface model
• entity model

Wireframe model

Use the vertices and edges of a shape to represent an object

• The method and model are simple , Easy to handle , With graphic display 、 The advantage of being easy to modify ;
• No face information , Cannot represent an object with a curved surface , The relationship between a given point and an object cannot be clearly defined , Unable to deal with many important problems ;
• Auxiliary tools for two-dimensional drawing or other methods .

Surface model

The surface of a body formed by directed edges , Express the corresponding shape with the geometry of the surface

• Able to express complex sculpted surfaces , It plays an important role in geometric modeling , For 3D solid models that support surfaces , It's the foundation ;
• extensive use ： Design of complex surfaces such as vehicles and molds ;
• Still can not fully express the shape of the object , The resulting shape description is difficult to be directly used in physical property calculation , It is difficult to guarantee the consistency and validity of object description ;
• It is impossible to examine the nature of the interrelationship between objects .

entity model

Define some basic voxels , And they are combined into complex geometric bodies through set operation

• It can completely represent all the shape information of the object , It can be unambiguously determined that a point is outside the object 、 Inside or on the surface ;
• Physical properties can be calculated 、 Finite element analysis 、 Eliminate hidden faces and cut shapes , Can further satisfy CAD/CAM And other applications