Mathematica:删除图形基元 [英] Mathematica: Removing graphics primitives

问题描述

鉴于 g 是一个带有诸如 Lines 和 Polygons 之类的基元的图形对象，您如何删除其中的一些?要向现有图形对象添加更多基元，我们可以使用 Show，例如: Show[g, g2] 其中 g2 是另一个图形对象与其他原语.但是如何删除不需要的原始对象呢?看看下面的

Given that g is a graphics object with primitives such as Lines and Polygons, how do you remove some of them? To add more primitives to an existing graphics object we can use Show, for instance: Show[g, g2] where g2 is another graphics object with other primitives. But how do you remove unwanted primitive objects? Take a look at the following

ListPlot3D[{{0, 0, 1}, {1, 0, 0}, {0, 1, 0}, {1, 1, 0}}, Mesh -> {1, 1}]

现在，对于输入表单:

InputForm[
   ListPlot3D[{{0, 0, 1}, {1, 0, 0}, {0, 1, 0}, {1, 1, 0}}, Mesh -> {1, 1}]
 ]

要从此对象创建线框，我们要做的就是移除多边形.另外，我们还可以移除顶点法线，因为它们对线框没有贡献.

To create a wire frame from this object all we have to do is remove the polygons. As an extra we can also remove the vertex normals since they don't contribute to the wireframe.

请注意，要制作线框，我们可以简单地设置 PlotStyle ->None 作为 ListPlot3D 中的一个选项.这摆脱了 Polygons 但不会删除 VertexNormals.

Notice that to make a wireframe we can simply set PlotStyle -> None as an option in ListPlot3D. This gets rid of the Polygons but doesn't remove the VertexNormals.

澄清问题.鉴于

 g = ListPlot3D[{{0, 0, 1}, {1, 0, 0}, {0, 1, 0}, {1, 1, 0}}, Mesh -> {1, 1}]

如何从 g 中删除一些图形基元，以及如何删除一些选项，即 VertexNormals?注意:选项 VertexNormals 是 GraphicsComplex 的一个选项.

How do you remove some of the of the graphics primitives from g and how do you remove some of the options, i.e. VertexNormals? Note: option VertexNormals is an option of GraphicsComplex.

如果这是不可能的，那么下一个问题可能是，您如何获取用于生成 g 的数据，以使用从 g 获得的一些数据生成新的图形对象.

If this is not possible then maybe the next question would be, how do you obtain the data used to generate g to generate a new graphics object with some of the data obtained from g.

推荐答案

一种方法是使用转换规则.鉴于你的

One way is to use transformation rules. Given your

im = ListPlot3D[{{0, 0, 1}, {1, 0, 0}, {0, 1, 0}, {1, 1, 0}},  Mesh -> {1, 1}]

你可以这样做

newim = im /. {_Polygon :> Sequence[], (VertexNormals -> _) :> Sequence[]}

或者，更紧凑地使用 Alternatives:

or, more compactly using Alternatives:

newim = im /. _Polygon | (VertexNormals -> _) :> Sequence[]

您也可以使用 DeleteCases 来获得类似的效果:

You could also use DeleteCases to get a similar effect:

newim = DeleteCases[im, (_Polygon | (VertexNormals -> _)), Infinity]

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