【Tips for advanced users–给高级用户的建议– 材质模块 – Houdini帮助文档中文版】
In large productions, making materials HDAs has several advantages.
对于大型的产品，制作材质的HDAs有几个优点：
It is possible to change the material HDA and have all .hip files automatically pick up the changes.
–可以改变材质的HDA，并且让所有.hip文件自动拾取这些改变。
It is possible to swap materials by adjusting the HOUDINI_OTL_PATH.
–通过调节HOUDINI_OTL_PATH路径来交互材质。
Note
Using material overrides largely breaks this work-flow since the overrides cannot be changed outside the .hip file.
–使用材质覆盖会很大程度上打断这个工作流程，因为因为这些覆盖不可以在外部hip文件中被改变。
Default Object Properties–默认的物体属性
Houdini is initially set up to assume that mantra is the primary renderer. If your studio uses a different primary renderer, it may be more useful to have a different set of initial object properties.
–Houdini会初始化设置，假定Mantra为首要的渲染器。如果你的工作室需要使用一个不同的渲染器 ，物体具有一组不同的初始属性可能是很有帮助的。
The creation script adds properties to the object using the oppropertycommand when an object is added. You can change this creation script. The opproperty command uses the parameter lists defined in $HH/soho/parameters. Since all of these files are searched using the default Houdini path and support include files, it is possible to customize the initial set of properties.
—-opproperty创建脚本会添加属性到物体上。你可以改变这个创建脚本。opproperty命令会使用在$HH/soho/parameters中定义的参数列表。由于所有这些文件的搜索是使用默认的Houdini路径，且支持包含的文件，所以可以自定义属性的初始化。
For example, to customize which parameters are defined on a geometry object, you might create $HOME/houdini9.0/soho/parameters/IFDmantra9.0.user.ds which has contents that look like the following:
—-例如，要自定义哪些参数是被定义在几何体上的，你可以创建$ HOME / houdini9.0 / soho /parameters/ IFDmantra9.0.user.ds,看上去就像下面的内容:
//
// Included when defining mantra parameters
//
#define USER_DEFINED_IFD_GEOMETRY_PARMS
parm {
name default_geometry
label "Default Geometry"
parmtag { spare_category "__spare_parmlist" }
parmtag { spare_parmlist "categories lightcategories
reflectcategories" }
}
This will change the default object to only have three rendering properties: categories, lightcategories and reflectcategories.
—这会改变默认物体，使其只有三个渲染属性： categories, lightcategories 和reflectcategories.
