Manual/PartII/Booleans
Wikipedia，自由的百科全书
Contents |
Booleans
布尔操作
Boolean operations can only be performed on mesh type objects --often called operands. The boolean tool will display an error message if only one mesh object is selected; see (Select error).In most cases the boolean operations are applied against solid, or closed, mesh objects with a well defined interior and exterior surface.
布尔操作是只能用于网格对象的特殊操作。虽然它们可以作用于所有网格对象，但是实际上它们被有意用于那些有着明确定义的内外表面区域的封闭实体。因此，一致地地定义每个对象的法线非常重要，也就是说每一个表面的每一条发现都应该指向外。
The boolean operations rely heavily on the surface normals of each object and so it is very important that the normals are defined properly and consistently. This means each object's normals should point outward. A good way to see the object's normals is to turn on the visibility of normals using the Mesh Tool 1 panel; the panel is accessable from the Buttons window, using F7 and clicking Draw normals. The normals are only visible while in Edit mode. (Visible normals) is an example of a cube with its normals visible. See The_Interface for a full description of the Mesh Tool 1 panel.
In the case of open objects, that is objects with holes in the surface, the interior is defined mathematically by extending the boundary faces of the object to infinity. As such, you may find that you get unexpected results for these objects. A boolean operation never affects the original operands, the result is always a new object. Some operations will require you to move the operands to see the results of the boolean operation.
对于开放对象，其内表面被算术地定义为延伸对象表面的边界到无限。在这种对象上你可能会得到无法预料的结果。布尔操作绝不会影响到原先的运算对象，其结果总是产生一个新的Blender对象。
The number of polygons generated can be very large compared to the original meshes, especially when using complex concave objects. Furthermore, the polygons that are generated can be of poor quality, for example, very long and thin and sometimes very small. Try using the Mesh Decimator (EditButtons F9) to fix this problem.
Vertices in the resulting mesh that fall on the boundary of the two original objects often do not match up, and boundary vertices are duplicated. This is good in some respects because it means that you can select parts of the original meshes by selecting one vertex in the result and pressing the select linked button (LKEY). This is handy if you want to assign materials and such to the result.
Sometimes the boolean operation can fail with a message saying ("An internal error occurred -- sorry"). If this occurs, try to move or rotate the objects just a very small amount.
Boolean operations only works on two mesh type objects. If more than two mesh objects are selected only the active and previously selected object are used as operands. The boolean operations also take Materials and UV-Textures into account, producing objects with Material indices or multi UV-mapped objects.
布尔操作可以通过明确选择两个网格对象然后按WKEY来启动，在弹出式菜单里有三种布尔操作可以选择，相交、合并和相减。布尔操作也会考虑材质和UV--纹理，产生带有材质索引的对象或者多重UV--映射的对象。
Booleans tool menu
To access the boolean operations use the WKEY while in Object mode. This shows the (Boolean operations) popup menu with the following choices:
- Intersect - operation creates a new object whose surface encloses the volume common to both original objects.
Intersect操作创建一个新的对象，其表面把原先的两个对象的公共体积部分包围。
- Union - The operation creates a new object whose surface encloses the volume of both original objects.
Union操作创建一个新的对象，其表面把原先的两个对象都包围。
- Difference - The operation is the only one in which the order of selection is important. The active object (pink in wireframe view) is subtracted from the selected object. That is, the resulting object surface encloses a volume which is the volume belonging to the selected and inactive object, but not to the selected and active one.
Difference操作是唯一一个跟对象的选择顺序有关的操作。激活对象（线框模型中为浅紫色）从选择对象中被减去。也就是说，生成对象的表面包围了属于选择的非激活对象而不属于选择的激活对象的那部分体积。
- Add Intersect Modifier - This is a short hand method that applys a modifier of type boolean and selects Intersect all in one step.
- Add Union Modifier - This is a short hand method that applys a modifier of type boolean and selects Union all in one step.
- Add Difference Modifier - This is a short hand method that applys a modifier of type boolean and selects Difference all in one step.
| Note: Boolean modifiers have much more flexibility than applying a boolean operation directly to the operands. |
Intersect
As mentioned above the Intersection of two objects produces a volume from the common volumes of the operands. Once the boolean is applied a completely new mesh object is created. (Intersect Before) is an example of a cube and sphere with Intersect operation applied. In order to see the results it is necessary to move the original operands out of the way; see (Intersect After).
 Intersect Before |  Intersect After |
The cube and the sphere have been moved to reveal the new volume created, labeled "A". Each face of the new object has the material properties of the corresponding surface that contributed to the new volume based on the Intersect operation.
The downside to using this tool is that in order to change the intersection, or even apply a different operation, you need to remove the new volume and reapply the operation.
Intersect as a modifier
There is a much more versatile way of performing an intersection that has greater flexibility and that is to apply the intersection as a Modifier; see (Boolean operations) option Add Intersect Modifier. As a modifier the intersection can participate in the modifier stack which means it can be enabled/disabled or even the order rearranged in the stack. In addition, you can move the operands and see the boolean operation applied interactively in realtime!
| Caution: if the operands' meshs are two complex you may be waiting a while as the system catches up with all the mouse movements. Turning off interactive display in the modifier panel can improve performance; see field labeled "D" in (Modifier stack). |
In order to apply the boolean modifier at least two mesh objects need to be selected. The active object will be the object that will receive the modifier and will become invisible. (Intersect Modifier) is an example of the Add Intersect Modifier applied. The cube has become invisible but you can still see the cube's object center, labeled "A".
To get the final volume created you need to apply the modifier using the modifier's Apply button and to see the volume you need to move the remaining operand away. Until you apply the modifier a new mesh object will not be created. When you apply the boolean modifier you are notified that any mesh sticky information, animation keys and vertex information will be deleted; see (Apply notification).
Modifier Stack
Once the boolean modifier has been applied the modifier stack will show the new modifier. (Modifier stack) is the modifier stack after the boolean Intersect has been applied. The modifier stack is visible in the Button Window under Editing-(F9) context panel group, when in Edit mode; see (Modifier stack). The modifier fields are:
- A - Boolean operation type. The choices are the same as using the WKEY.
- B - Modifier name. This will always be boolean when the modifier was added using the WKEY.
- C - Enables/Disables the modifier during rendering.
- D - Enables/Disables the modifier in the 3D window. This is helpful if the mesh operands are very complex and interactive perform is unacceptable.
- E - If more than one modifier is present you can move the modifier up or down the stack.
- Apply - This takes the modifier, in its current state, and applies it and then removes it from the stack. This is typically the last thing done to get the final results.
- Copy - Copy the modifier and places it below this modifier.
- To - You can redirect the application of this modifier to another mesh type object.
- Add Modifier - Add another modifier to the modifier stack. For example, you can add the Decimate modifier to help reduce vertex and face counts.
Union
As mentioned above the Union of two objects produces a volume from both volumes of the operands. Once the boolean is applied a completely new mesh object is created. (Union example) is an example of a cube and sphere with Union operation applied. In order to see the results it is necessary to move the original operands out of the way.
The cube and the sphere have been moved to reveal the new volume created, labeled "U". "U" is now a single mesh object and the faces of the new object have the material properties of the corresponding surface that contributed to the new volume based on the Union operation.
As will with the Intersect operation, the Union operation can be applied as a modifier as well with the same functionality as the Intersect modifier. See Intersect modifier and Modifier Stack for further details.
Difference
As mentioned above the Difference of two objects is not commutative in that the active object minus the inactive object does not produce the same as inactive minus active. Once the boolean is applied a completely new mesh object is created. (Difference example) is an example of a cube subtracted from a sphere (i.e. the cube's volume has been subtracted from the sphere's volume). In order to see the results it is necessary to move the original operands out of the way.
The cube and the sphere have been moved to reveal the new volume created, labeled "D". "D" is now a single mesh object and the faces of the new object have the material properties of the corresponding surface that contributed to the new volume based on the Difference operation. "D"'s volume is less than "B"'s volume because it was decreased by subtracting part of the cube's volume.
As will with the Intersect operation and the Union, the Difference operation can be applied as a modifier with the same functionality as the Intersect and the Union modifier. See Intersect modifier and Modifier Stack for further details.
|
Blendercn need your support.
中国CG事业需要你的支持.
Please cherish the people you create a learning environment.
请珍惜他人为你创造的学习环境.
