Overview概述

Maya XGen is a geometry instancer that lets you populate the surface of polygon meshes with an arbitrary number of primitives either randomly or uniformly placed. XGen lets you procedurally create and style hair, fur and feathers for characters. For set dressing, XGen lets you quickly populate large-scale environments, including grass savannas, forests, rocky landscapes, and debris trails.

Maya XGen是一種幾何體替代技術。通過它，用戶可以在多邊形物體上創建隨機分布或者均勻分布的巨量物體單元（Primitive）。使用XGen，我們可以通過程序來為角色創建毛髮、毛和羽毛，並進行梳理和造型設計。還可以使用XGen來創建諸如：草原、林地、山石及石子小路等等場景。

Primitive Types物體單元類型

Splines控制曲線

Spline primitives are curves made up of two or more segments. Use Splines for fur,

simple stiff shapes, and complex ribbon shapes like long or curly hair.

Spline Primitives是由兩節或兩節以上線段組成的曲線。Spline適用於製作短毛、簡單堅硬物體、長毛、捲髮或類似的複雜織物。

Cards無厚度面

Card primitives define individual NURBS planes that attached to the patch at the plane pivot point.

無厚度面片使用NURBS面做單元，創建後，其Pivot中心會「粘貼」在Patch（即XGen生長面）上。

NOTE: This type is currently not supported.

注意當前還不支持這種類型

Sphere球體

Sphere primitives define a sphere with controllable length, width, and depth.

選擇Sphere，意味著使用可控長度、寬度和深度的球體做Primitives單元

NOTE: This type is currently not supported.

注意：當前還不支持這種類型。

Archives文檔

Archive primitives are instances of Alembic-based geometry. You specify the archive geometry you want to instance by selecting an XGen archive (.xarc) file.

Archive方式是一種Alembic-Based幾何體替代方式，你可以給Archive指定一個XGen Archive（.xarc）文件

NOTE: This type is currently not supported.

注意：當前還不支持這種類型。

XGen Splines Quickstart快速指南

This section will guide you through the creation of a basic XGen spline scene.

這個章節指導你創建一個簡單的XGen Spline（XGen控制曲線）場景。

Before we proceed, it is useful to unload the xgenMR.py plugin as this plugin assumes XGen is being used with Mental Ray and will result in more steps on our part to 「undo」 its effect. From the main menu, select Windows > Settings/Preferences > Plug-in Manager. Find xgenMR.py and unload it. If you don』t use Mental Ray, we recommend also turning off autoload.

在繼續講解之前，應該先卸載XgenMr.py插件，因為這個插件指定Xgen使用Mental Ray渲染器，導致我們需要用更多步驟去取消這個預設。從主菜單，選擇Windows > Settings/Preferences > Plug-in Manager.找到XgenMR.py，然後卸載它。如果你用不MentalRay渲染器，建議你關掉自動載入。

Start with an empty scene and add a polygon plane at the origin 25 x 25 Maya units in size. You can do this 「manually」, or run the following MEL:

開啟一個空場景，創建一個25 X 25 Maya單位的多邊形平面，你可以手動創建這些，或者運行下面MEL腳本

file -f -new; polyPlane -w 25 -h 25 -sx 10 -sy 10 -ax 0 1 0 -cuv 2 -ch 1;


Bring up the XGen window (aka XGen description editor). You can either click the Open the XGen button on the XGen shelf (first button from the left), or select XGen > Open the XGen Window from the main menu (Maya 2015) or select Generate

> XGen Editor from the Modeling menu set (Maya 2016). Alternatively, you can run the MEL command XgCreateDescriptionEditor.

開啟XGen窗口（也叫XGen Description editor）。你可以通過點擊XGen工具架上的按鈕（最左邊的按鈕）打開XGen，或者選擇從Maya2015的主菜單中選擇XGen > Open the XGen

With our Plane still selected,click Create New Description in the XGen Window to display the Create XGen Description window.

選擇剛才創建的平面，在XGen窗口點擊Creat XGen Description來顯示Create XGen Description窗口。

Change the description name to RsQuickStartDescription and the collection name to RsQuickStartCollection, leave the other settings at their defaults and click Create. Open the Outliner and notice the DAG nodes that were created.

修改描述名字為RsQuickStartDescription並且修改Collection名字 RsQuickStartCollection，保持其他設置為默認，點擊Create，打開大綱視圖，注意查看我 創建的DAG節點。

ur original polygon plane has been 『bound』 to the newly created description and is

therefore now also considered a piece of 『control geometry』 for XGen.

我們創建的原始平面與新創建的Description（描述）節點建立了關聯，因此，它就是XGen的「控制幾何體」。

The collection (RsQuickStartCollection) is essentially a container for descriptions. In this example we have a single description, RsQuickStartDescription.

這個Collection（節點集，RsQuickStartCollection）是Description節點的核心容器。這個例子中，我們只有一個Description節點，叫做RsQuickStartCollection。

The description holds all the procedural parameters to describe the generated

splines. In a non-trivial scene, you could have a number of descriptions, each describing a different 『type』 or 『look』 of splines. For example, you might have a description for a character』s head hair, another for the character』s body hair and a third for the character』s facial stubble.

這個Description節點包含了所有用於控制生成Splines的程序參數描述。對於稍微複雜一些的場景，可能會有很多的Description節點，用於描述同不「類型」或者「形狀」的Splines。例如，可能會為角色頭髮創建一些Description節點，身體毛髮是另外一個Description節點，還有可能給角色面部的鬍子創建一個Description節點。

Parented under each description are patches, one patch per bound geometry. The

patches are named <geometry>_<description> and represent the XGen splines that the given description will generate for the given geometry.

在每個Description節點中，還會包含一些Patch（毛髮生長塊）子節點。每個Patch節點對應一個關聯的幾何體。這些Patch節點會以<geometry>_<description>的形式來命名，他們告訴XGen Spline，在那些選定的幾何體生長Description節點描述的毛髮。

In this trivial example, we have a single piece of control geometry bound to a single description and therefore we have a single patch. In general, you could have multiple descriptions each bound to several pieces of control geometry and any single piece of control geometry can be bound to multiple descriptions.

這個簡單的例子中，我們只有一個Description節點關聯在一個控制幾何體上，因此只有一個Patch節點對應。通常，你可以有多個Description節點關聯多個控制幾何體，任何一個控制幾何體也可以關聯多個Description節點。

Now, back to the XGen description editor, switch to the Preview/Output tab and in the Output Settings section, change the Renderer to Redshift. Since Redshift does not have any unique XGen description attributes, this step is not strictly necessary, but that may change in the future so it』s good practice.

我們再看看XGen Description編輯器，切換Preview/Output欄，在Output Settings的Render部分選擇Redshift。Redshift並沒有特別的XGen屬性，因而這一步現在不是必須的，但是將來可能會有變化，所有這們做是一個好習慣。

Now render the scene (make sure Redshift is the active scene renderer).

現在渲染這個場景（首先，確保Redshift是激活的渲染器）。

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