Introduction subdivision surfaces
In the field of three-dimensional modeling, subdivision surfaces can be considered a more common term, often used for prototyping animated character, even in the field of industrial design, also became popular with the subdivision modeling to prototyping. Textbooks mentioned a subdivision surface is bound to mention "Geri's Game", is a subdivision surface technology this cartoon character modeling applications.
So what exactly is the subdivision surfaces it? Sketch of a child, the beginning must learn to draw a circle. Generally start from square, then continue to cut corners, and finally became a circle. This is actually a subdivision curve. Such mapping method, the image may be referred to as a polishing method of cutting: designer first outline the contours of the object substantially, and then continuously refined by cutting corners.
The method is extended to three-dimensional circle, you get drawn from the ball.
Application of subdivision surfaces do three-dimensional model of the prototype design is very convenient. Typically requires only two steps, first create a substantially contour model, then set-point line to be cut. For example, the table this model, first create a profile of its model, looks very simple, which then set point line to be cut.
Core subdivision surface on one point: subdivision rules. Different subdivision rules, the resulting subdivision surface shape is different. Common rules have Catmull-Clark subdivision subdivision, Doo-Sabin subdivision, Loop subdivision and so on. Specific subdivision rules can refer to textbooks or relevant papers.
Above we talked about, subdivision surfaces can be applied to prototyping. The main features are simple to use and also very rich expressive. Further, general industrial design software is used to represent the curved surface spline surfaces (piecewise polynomial surface), which belongs to a continuous representation information, when used in manufacturing, the surface needs to be discretized. For example, 3D printing manufacturing, its input is a grid. Modeling subdivision, the mesh can be obtained directly, does not require such an intermediate curved bar represents a sample format.
On the card, there are also applications for subdivision surfaces. In the game scene, since the number of real-time requirements, the mesh patch to be as low as possible requires, however, fewer grid, less the details of the model. In order to enhance the number of grid as much as possible, the graphics rendering pipeline added Tessellation module, this module directly on the hardware of the grid has been subdivided.
细分建模产生的网格，其面片分布非常的规则(regular)。规则的网格不管是用于几何处理，还是用于有限元计算，都有非常好的性质，比如计算稳定性。另外，细分网格表示的数据量非常小，很适合于网络传输。
细分网格建模
三维公园提供了在线的三维建模工具，用户可以直接在浏览器中进行三维设计。细分建模主要面对人群是普通的三维设计爱好者，不需要专业的三维设计知识，就能快速上手进行三维建模。用户创建的模型，可以直接导出进行3D打印，注册用户也可以在线保存自己的三维设计。
建模工具采用了最新的浏览器3D技术：WebGL，它是HTML5标准中的3D技术。目前浏览器对WebGL已经有了很好的支持了，常见的浏览器如Chrome，Firefox，Safari，Opera，以及国内的搜狗浏览器，猎豹浏览器，360安全浏览器，傲游浏览器，2345王牌浏览器等，都能很好的支持WebGL。相信将来Web3D将会给Web带来更加炫酷的用户体验。
细分建模的核心操作就三个：拉伸，变换，光滑。这三个操作的简单组合，就能创建出常见的三维模型。拉伸操作通过简单面挤出就能创建出新的模型部件，比如这个桌子，就是通过一个box，经过一系列的拉伸操作得到的。
光滑操作可以改变模型的局部光滑性，与整体细分不同的是，它的指定是局部的，可以保持住一些尖锐的几何部分。我们给这个方桌子指定光滑性后，就得到了这个漂亮的桌子模型。
用户创建的三维模型，可以导出来(STL, OBJ格式)进行3D打印。注册用户也可以在线存储自己的三维设计。用户可以在线浏览三维公园里的三维设计，注册用户甚至可以在已有的设计基础上进行修改，这就是模板设计，不需要从零开始做设计。设计回放功能，可以栩栩如生的回放设计过程，在回放过程中，我们可以学习到别人的设计设计思路，比如这个飞机的设计回放：
For anyone interested in three-dimensional modeling, you can go try subdivision modeling . Whether you are a professional designer, or an ordinary enthusiast, you can show your design creativity.