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The main difference between polygonal and NURBS modeling is the way the mesh is calculated by the computer.
多边形建模和 NURBS 建模之间的主要区别在于计算机计算网格的方式。
For polygon modeling it calculates polygons, which are flat planes that comprise a 3D shape (the way that a cube is made out of 6 squares for example).
对于多边形建模，它计算多边形，多边形是构成3D形状的平面（例如，立方体由6个正方形组成的方式）。
NURBS calculates the mesh as splines between points, which can make curves out of a single section of geometry.
NURBS 将网格计算为点之间的样条曲线，从而可以从几何图形的单个截面中生成曲线。
NURBS (which is shorthand for Non-Uniform Rational B-splines) uses complex mathematics to calculate the surface of a model. This means that it is far better suited for models where a high degree of accuracy is needed.
NURBS（非一致有理 B 样条的简写）使用复杂的数学来计算模型的曲面。这意味着它更适合需要高精度的模型。
A good example where this is important is in engineering. When an engineer is trying to work out the aerodynamics of a plane or car, and they want to run tests in a digital wind tunnel.
这很重要的一个很好的例子是工程学。当工程师试图计算飞机或汽车的空气动力学时，他们希望在数字风洞中进行测试。
The downside of this highly mathematical way of calculating a model’s size is that it becomes more difficult for the computer to calculate, which means that it is unsuited for applications where render times need to be fast.
这种高度数学化的模型大小计算方法的缺点是计算机变得更加难以计算，这意味着它不适合渲染时间需要快速的应用程序。


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You would never find NURBS surfaces in video games, for example (at least at the time of writing).
例如，你永远不会在视频游戏中找到NURBS表面（至少在撰写本文时）。
In polygonal modeling it is impossible to make a perfectly smooth curve, due to the fact they are always calculated as a straight line between points.
在多边形建模中，不可能形成完全平滑的曲线，因为它们总是被计算为点之间的直线。
However, using smoothing groups and a high number of polygons, you can make sections that are perceived as a smooth curve on the screen.
但是，使用平滑组和大量多边形，可以创建在屏幕上被视为平滑曲线的截面。
NURBS have the additional benefit of being a smaller file size, as all the data contained are mathematical points. This also means the data is easy to read and understand between different programs so you never end up with corrupted meshes, like can happen when transferring polygonal models.
NURBS的另一个好处是文件大小较小，因为包含的所有数据都是数学点。这也意味着数据在不同程序之间易于阅读和理解，因此您永远不会像传输多边形模型时那样最终导致网格损坏。
When Are NURBS Used?
何时使用 NURBS？
I’m sure you’re thinking this all sounds great! Why don’t we use NURBS more often?
我相信你认为这一切听起来都很棒！我们为什么不更频繁地使用 NURBS？
That’s because I have yet to go into the limitations behind NURBS, which there are many.
这是因为我还没有深入研究NURBS背后的局限性，NURBS有很多。
NURBS objects are only ever 4 sided. This is a limitation to the fact that a Polygon is usually an N-gon consisting of any number of sides up from 3.
NURBS 对象只有 4 面。这是对多边形通常是 N 形的限制，该 N 形由任意数量的边组成，从 3 开始。
This makes the process of modeling with polygons a much simpler process. Expanding on this polygon modeling is a lot easier to manipulate and change, which again makes for far easier construction of meshes.
这使得使用多边形建模的过程变得更加简单。在此多边形建模上进行扩展更易于操作和更改，这再次使网格的构建变得更加容易。
NURBS objects are always separate from each other as well, making them difficult to attach together for one model.
NURBS 对象也始终彼此分离，因此很难将它们附加到一个模型上。
Due to their perfect calculations of curvature and position, this means you will never see the seams between them. But it is still a limitation in their workflow. If you wish to animate a NURBS object, you would first need to convert it into a polygonal mesh so that you can weld joints together so they will not come apart.
由于它们对曲率和位置的完美计算，这意味着您将永远不会看到它们之间的接缝。但这仍然是他们工作流程中的一个限制。如果要对 NURBS 对象进行动画处理，首先需要将其转换为多边形网格，以便可以将接头焊接在一起，以免它们分开。
It is also not possible to UV unwrap a NURBS object.
也无法通过 UV 对 NURBS 对象进行包装。
For this reason, if it’s a model you need to texture, it is better to use a polygon mesh. That way you have the ability to adjust how it’s projected onto the mesh.
因此，如果它是需要纹理的模型，则最好使用多边形网格。这样，您就可以调整投影到网格上的方式。

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To summarize: the difference between NURBS and polys can be compared roughly to the differences between vector and rasterized images in 2D.
总而言之：NURBS和多边形之间的差异可以大致与2D中矢量和栅格化图像之间的差异进行比较
Vector images also use mathematical data points to make incredibly accurate images that are often used for logos and marketing, but can be limited in what you can do with them.
矢量图像还使用数学数据点来制作令人难以置信的准确图像，这些图像通常用于徽标和营销，但您可以对其进行处理可能会受到限制。
In comparison, raster images use pixels that make them easier to work with, and have more tools at their disposal for editing & manipulation.
相比之下，光栅图像使用像素，使它们更容易使用，并且有更多的工具可供编辑和操作。
Due to the benefits that NURBS bring to the table, most modern 3D packages utilise NURBS in some way.
由于NURBS带来的好处，大多数现代3D软件包都以某种方式利用NURBS。
They are usually converted to polygons later in the production process, but NURBS are very good at making the initial base mesh.
它们通常在生产过程的后期转换为多边形，但NURBS非常擅长制作初始基础网格。

Image source
图片来源
The main difference between polygonal and NURBS modeling is the way the mesh is calculated by the computer.
多边形建模和 NURBS 建模之间的主要区别在于计算机计算网格的方式。
For polygon modeling it calculates polygons, which are flat planes that comprise a 3D shape (the way that a cube is made out of 6 squares for example).
对于多边形建模，它计算多边形，多边形是构成3D形状的平面（例如，立方体由6个正方形组成的方式）。
NURBS calculates the mesh as splines between points, which can make curves out of a single section of geometry.
NURBS 将网格计算为点之间的样条曲线，从而可以从几何图形的单个截面中生成曲线。
NURBS (which is shorthand for Non-Uniform Rational B-splines) uses complex mathematics to calculate the surface of a model. This means that it is far better suited for models where a high degree of accuracy is needed.
NURBS（非一致有理 B 样条的简写）使用复杂的数学来计算模型的曲面。这意味着它更适合需要高精度的模型。
A good example where this is important is in engineering. When an engineer is trying to work out the aerodynamics of a plane or car, and they want to run tests in a digital wind tunnel.
这很重要的一个很好的例子是工程学。当工程师试图计算飞机或汽车的空气动力学时，他们希望在数字风洞中进行测试。
The downside of this highly mathematical way of calculating a model’s size is that it becomes more difficult for the computer to calculate, which means that it is unsuited for applications where render times need to be fast.
这种高度数学化的模型大小计算方法的缺点是计算机变得更加难以计算，这意味着它不适合渲染时间需要快速的应用程序。


Image source
图片来源
You would never find NURBS surfaces in video games, for example (at least at the time of writing).
例如，你永远不会在视频游戏中找到NURBS表面（至少在撰写本文时）。
In polygonal modeling it is impossible to make a perfectly smooth curve, due to the fact they are always calculated as a straight line between points.
在多边形建模中，不可能形成完全平滑的曲线，因为它们总是被计算为点之间的直线。
However, using smoothing groups and a high number of polygons, you can make sections that are perceived as a smooth curve on the screen.
但是，使用平滑组和大量多边形，可以创建在屏幕上被视为平滑曲线的截面。
NURBS have the additional benefit of being a smaller file size, as all the data contained are mathematical points. This also means the data is easy to read and understand between different programs so you never end up with corrupted meshes, like can happen when transferring polygonal models.
NURBS的另一个好处是文件大小较小，因为包含的所有数据都是数学点。这也意味着数据在不同程序之间易于阅读和理解，因此您永远不会像传输多边形模型时那样最终导致网格损坏。
When Are NURBS Used?
何时使用 NURBS？
I’m sure you’re thinking this all sounds great! Why don’t we use NURBS more often?
我相信你认为这一切听起来都很棒！我们为什么不更频繁地使用 NURBS？
That’s because I have yet to go into the limitations behind NURBS, which there are many.
这是因为我还没有深入研究NURBS背后的局限性，NURBS有很多。
NURBS objects are only ever 4 sided. This is a limitation to the fact that a Polygon is usually an N-gon consisting of any number of sides up from 3.
NURBS 对象只有 4 面。这是对多边形通常是 N 形的限制，该 N 形由任意数量的边组成，从 3 开始。
This makes the process of modeling with polygons a much simpler process. Expanding on this polygon modeling is a lot easier to manipulate and change, which again makes for far easier construction of meshes.
这使得使用多边形建模的过程变得更加简单。在此多边形建模上进行扩展更易于操作和更改，这再次使网格的构建变得更加容易。
NURBS objects are always separate from each other as well, making them difficult to attach together for one model.
NURBS 对象也始终彼此分离，因此很难将它们附加到一个模型上。
Due to their perfect calculations of curvature and position, this means you will never see the seams between them. But it is still a limitation in their workflow. If you wish to animate a NURBS object, you would first need to convert it into a polygonal mesh so that you can weld joints together so they will not come apart.
由于它们对曲率和位置的完美计算，这意味着您将永远不会看到它们之间的接缝。但这仍然是他们工作流程中的一个限制。如果要对 NURBS 对象进行动画处理，首先需要将其转换为多边形网格，以便可以将接头焊接在一起，以免它们分开。
It is also not possible to UV unwrap a NURBS object.
也无法通过 UV 对 NURBS 对象进行包装。
For this reason, if it’s a model you need to texture, it is better to use a polygon mesh. That way you have the ability to adjust how it’s projected onto the mesh.
因此，如果它是需要纹理的模型，则最好使用多边形网格。这样，您就可以调整投影到网格上的方式。

更多精彩图片 请登录

Image source
图片来源
To summarize: the difference between NURBS and polys can be compared roughly to the differences between vector and rasterized images in 2D.
总而言之：NURBS和多边形之间的差异可以大致与2D中矢量和栅格化图像之间的差异进行比较
Vector images also use mathematical data points to make incredibly accurate images that are often used for logos and marketing, but can be limited in what you can do with them.
矢量图像还使用数学数据点来制作令人难以置信的准确图像，这些图像通常用于徽标和营销，但您可以对其进行处理可能会受到限制。
In comparison, raster images use pixels that make them easier to work with, and have more tools at their disposal for editing & manipulation.
相比之下，光栅图像使用像素，使它们更容易使用，并且有更多的工具可供编辑和操作。
Due to the benefits that NURBS bring to the table, most modern 3D packages utilise NURBS in some way.
由于NURBS带来的好处，大多数现代3D软件包都以某种方式利用NURBS。
They are usually converted to polygons later in the production process, but NURBS are very good at making the initial base mesh.
它们通常在生产过程的后期转换为多边形，但NURBS非常擅长制作初始基础网格。