Relativity SCAD不是独立语言，只是OpenSCAD的library，但是它提供了一套全新的API替换掉OpenSCAD原有的API的大部分功能，使用起来比OpenSCAD API简单很多。

特别之处：

• 通过描述对象之间的相对位置，大大简化了OpenSCAD建模中繁琐的transformation
• 通过selector对部分对象进行操作，减少了boolean operation的繁琐组合

下载文件后，将其放在计算机上的 OpenSCAD 文件夹中。此文件夹的位置因操作系统而异。启动 OpenSCAD 并键入以下内容：

include <relativity.scad>

使用“include”关键字导入依赖很重要。relativity.scad 需要在其初始化期间声明变量。如果您使用“use”关键字导入 relativity.scad，OpenSCAD 将不会加载这些变量，并且会导致奇怪的行为！

这个 OpenSCAD 库增加了相对于其他几何基元的大小、位置和方向对象的功能。

为此，该库引入了一组新模块来替换 OpenSCAD 中的默认几何图元：

实体	新语法	老语法
	box	cube
	rod	cylinder
	ball	phere

如果您需要，所有原始几何图元仍然存在，您可以决定使用多少或多少使用它们。新的原语几乎具有旧版本的所有行为，但有两个重要区别。

First, in place of center is a new attribute, anchor. This attribute specifies where the axis of rotation is to be placed relative to the object. The anchor attribute is given as a vector whose elements range from -1 (e.g. bottom of axis) to 1 (e.g. top of axis). A value of 0 indicates the anchor is to be centered along an axis.
首先，代替中心的是一个新属性，锚点。此属性指定旋转轴相对于对象的放置位置。锚属性作为一个向量给出，其元素范围从 -1（例如轴的底部）到 1（例如轴的顶部）。值 0 表示锚点将沿轴居中。

	+1	0	-1
X	锚=[1,0,0]	锚=[0,0,0]	锚=[-1,0,0]
Y	锚=[0,1,0]	锚=[0,0,0]	锚=[0,-1,0]
Z	锚=[0,0,1]	锚=[0,0,0]	锚=[0,0,-1]

The second distinction among these new primitives allows for the creation of child objects. By default, a child object is positioned with its origin at the center of its parent:
这些新原语之间的第二个区别允许创建子对象。默认情况下，子对象的原点位于其父对象的中心：

box(50, anchor=[0,0,-1])
    sphere(d=55);
    

this however can be changed using of a second operation, align:

然而，这可以使用第二个操作来改变，对齐：

box(50, anchor=[0,0,-1])
    align([0,0,1])
    sphere(d=60);
    

You can align objects along any axis. The value passed to align() is a vector whose elements range from -1 (e.g. bottom of axis) to 1 (e.g. top of axis). A value of 0 indicates an object is to be placed at the center of its parent along that axis.

您可以沿任何轴对齐对象。传递给 align() 的值是一个向量，其元素范围从 -1（例如轴的底部）到 1（例如轴的顶部）。值 0 表示对象将沿该轴放置在其父对象的中心。

	+1	0	-1
X	对齐([1,0,0])	对齐([0,0,0]	对齐([-1,0,0]
Y	对齐([0,1,0]	对齐([0,0,0]	对齐([0,-1,0]
Z	对齐([0,0,1]	对齐([0,0,0]	对齐([0,0,-1]

You can also pass a list of vectors. When you pass a list of vectors, align() will create duplicates of its children in the locations indicated by your vectors.

您还可以传递向量列表。当您传递向量列表时， align() 将在向量指示的位置创建其子项的副本。

box(50, anchor=[0,0,-1])
    align([[0,0,1], [0,1,0]])
    sphere(d=60);
    

The examples above use sphere() as their child object. However, ball() can also be be used as a child. Using ball() will allow us to combine align() and anchor, making it easy to stack objects end-to-end:

上面的示例使用 sphere() 作为它们的子对象。但是，ball() 也可以用作子级。使用 ball() 将允许我们结合 align() 和锚点，使端到端堆叠对象变得容易：

box(50, anchor=[0,0,-1])
align([0,0,1])
ball(50, anchor=[0,0,-1])
align([0,0,1])
rod(50, anchor=[0,0,-1]);

To allow for readable code, relativity.scad comes with a few constants representing commonly used values for the align operator:

为了允许代码可读，relativity.scad 带有一些常量，表示对齐运算符的常用值：

top = [0,0,1];
center=[0,0,0];
bottom = [0,0,-1];
x = [1,0,0];
y = [0,1,0];
z = [0,0,1];

It is also possible to combine this constant with + or - operators, since OpenSCAD does (simple) vector calculations.

也可以将此常数与 + 或 - 运算符结合使用，因为 OpenSCAD 进行（简单）矢量计算。

There are also two special variables that are exposed by the align() module, $inward and $outward. $inward points towards the center of a parent object, while $outward points away from it.

align()对齐模块还公开了两个特殊变量，$inward 和 $outward。 $inward 指向父对象的中心，而 $outward 指向远离它的对象。

The anchor parameter defaults to $inward. This is meant to facilitate stacking objects. All told, the code above can be rewritten:

锚参数默认为 $inward。这是为了便于堆叠对象。总而言之，上面的代码可以重写：

box(50)
align(top)
ball(50)
align(top)
rod(50);

Child objects by default will maintain the same z-axis orientation as their parent objects

默认情况下，子对象将保持与其父对象相同的 z 轴方向

box(50, anchor=[0,0,-1])
align([0,1,0])
rod(d=50, h=50, anchor=[0,-1,0]);

This, however, can be changed with the use of another module, orient. The orient module will redirect the top of a child object to face a given direction. Sometimes rotation using orient can be more intuitive than using rotate

然而，这可以通过使用另一个模块 orient 来改变。 orient 模块将重定向子对象的顶部以面向给定方向。有时使用 orient 进行旋转比使用 rotate 更直观

box(50, anchor=[0,0,-1])
align([0,1,0])
orient([0,1,1])
rod(d=50, h=50, anchor=[0,0,-1]);

You can also pass a list of vectors to orient. In this case, orient will create duplicates of its children with their tops facing the directions you specify in the list.

您还可以将向量列表传递给 orient。在这种情况下， orient 将创建其子项的副本，其顶部朝向您在列表中指定的方向。

//OpenSCAD logo:  
differed("hole", "not(hole)")  
ball(50)  
orient([x,y,z])  
rod(d=25, h=50, $class="hole");  

relativity.scad exposes a dynamic variable, $parent_size, in case there are any unforeseen circumstances where something needs to be done relative to a parent object. This can also be used when setting the size of a child, say, when creating a fractal:

relativity.scad 公开了一个动态变量 $parent_size，以防有任何不可预见的情况需要相对于父对象执行某些操作。这也可以在设置孩子的大小时使用，例如，在创建分形时：

box([50,50,50])
align(top)
box(0.8*$parent_size)
align(top)
box(0.8*$parent_size);

The tree demo provides a good example for the parent() and $parent_size functionality.

树演示为 parent() 和 $parent_size 功能提供了一个很好的示例。

To ease the use of $parent_size, geometric primitives for rod and ball accept size as their first parameter argument, much like cube and box.

为了简化 $parent_size 的使用，棒和球的几何基元接受大小作为它们的第一个参数参数，就像立方体和盒子一样。

rod([50,50,50])
align(top)
rod(0.8*$parent_size)
align(top)
rod(0.8*$parent_size);

An interesting consequence to this means you can pass rod and ball different values for x,y, and z:

一个有趣的结果意味着您可以为 x、y 和 z 传递不同的值：

rod([50,50,50])
align(top)
rod([$parent_size.x*.5, $parent_size.y*.7, $parent_size.z*.9])
align(top)
rod([$parent_size.x*.5, $parent_size.y*.7, $parent_size.z*.9]);

Another, more unfortunate side effect means rod does not currently support multiple diameters/radii through the d1 and d2 parameters. This may change as need arises. You can still use the original cylinder primitive when circumstances call for it, but a better idea might be to perform the hull between two rods, one of infinitesimal height.

另一个更不幸的副作用意味着杆目前不支持通过 d1 和 d2 参数的多个直径/半径。这可能会随着需要而改变。当情况需要时，您仍然可以使用原始圆柱体原语，但更好的想法可能是在两根杆之间执行船体，其中一根杆的高度非常小。

hulled() rod(d=30, h=infinitesimal) rod(d=10, h=20);

Relativity.scad transforms the way you work with objects in OpenSCAD. You'll find yourself working a lot more with “tree-like” structures, where geometric primitives nest inside one another. This is similar to the way you write using nested tags in html. Just like html, there is a system for performing operations on the tree-like structure. In html, there's css. In relativity, there's the CSG operations

Relativity.scad 改变了您在 OpenSCAD 中处理对象的方式。您会发现自己更多地使用“树状”结构，其中几何基元相互嵌套。这类似于您在 html 中使用嵌套标签编写的方式。就像 html 一样，有一个系统可以对树状结构进行操作。在html中，有css。在相对论中，有 CSG 操作：

Module	Demo	Code
differed		differed("hole","not(hole)") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
hulled		hulled("hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
intersected		intersected("hole", "not(hole)") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
show		show("hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
hide		hide("hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
colored		colored("red", "hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
scaled		scaled(0.95, "hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
resized		resized([47,47,47], "hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
mirrored		mirrored(y) rotated(22*z, class="hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
rotated		rotated(22*z, class="hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");
translated		translated(10*z, class="hole") ball(50) orient([x,y,z]) rod(d=25, h=50, $class="hole");

Selectors are the means through which CSG operations specify class. Selectors are strings whose format is meant to resemble a subset of CSS selector syntax.

选择器是 CSG 操作指定类的方法。选择器是字符串，其格式类似于 CSS 选择器语法的子集。

Illustrations below uses the following code:

下面的插图使用以下代码：

colored("blue", ...)
ball(50, $class="parent")
{
    align(x)
    ball(40, $class="child A")
    align(x)
    ball(30, $class="grandchild");
    
    align(z)
    ball(40, $class="child B")
    align(z)
    ball(30, $class="grandchild");
    
    align(-x)
    ball(40, $class="child C")
    align(-x)
    ball(30, $class="grandchild");
}

As of version 2015.02.14, selectors support the following syntax:

从 2015.02.14 版本开始，选择器支持以下语法：

Selector	Render	Description
Tree		A fractal tree rendered using parent() and mirrored() 使用 parent() 和 mirrored() 渲染的分形树
Stepper Motor		A high fidelity NEMA-17 stepper motor written in 50 lines of code 用 50 行代码编写的高保真 NEMA-17 步进电机
Motor Mount		A stepper motor mount made easy with attach() 使用 attach() 可以轻松安装步进电机
Human Body		A human body designed using techniques in classical figure drawing. Work in progress. Not for the faint-hearted. 使用古典人物绘画技术设计的人体。工作正在进行中。不适合胆小的人。
Flower
Centipede

https://github.com/davidson16807/relativity.scad/wiki