Wpf3D入门指南（WindowsPresentationFoundation（WPF）3。。。

Wpf3D⼊门指南
（WindowsPresentationFoundation（WPF）3。

The purpose of this tutorial is to provide the simplest explanation and examples possible of how to create 3D graphics with Windows Presentation Foundation (WPF) (formerly known as "Avalon"). It is not a comprehensive guide to 3D modeling, but simply a primer for those who have no knowledge of or experience with 3D graphics. 3D or vector-based graphics is a different world from 2D GDI, and it took a long period of guessing, stumbling, and trial and error before I understood what was going on with it. Ultimately I hope that you are able to avoid some of the pains I went through by reading through this tutorial.
这篇⽂章的⽬的是为如何⽤WPF（也就是以前的avalon技术）建⽴3D图形提供⼀个简单的解释并提供⼀些⽰例，它并不是全⾯的3D建模⼊门教程，仅仅是为那些没有3D图形经验或知识的同⾏提供⼀个简单的⼊门。

3D或基于⽮量的图形对于2D GDI来说是⼀个不同的世界，⼤部分时间我经历了猜测，困惑，实验和错误，直到我理解了我们正在⽤它做什么。

最后我希望你读过这篇⽂章後，可以避免⼀些我曾经经历的错误。

For your convenience, the tutorial contains inline links to the documentation of all of the .Net 3.0 classes, structures, properties, and methods used in the example code. Click away as you please.
为了您的⽅便，这篇指南包括了链接，这些链接链向所有在⽰例代码中⽤到的关于.NET 3.0的类，结构，属性及⽅法，随便你去点击。

Disclaimer
不承诺
While I make my best effort to make sure the content and examples in this tutorial are accurate and bug-free, I'm not responsible for anything bad (e.g. crashes, loss of data, any damage) that may happen if you use the information or code in this tutorial. I'll do my best to make sure bugs are fixed and that the content is as accurate as possible. In short, have some common sense and use this at your own risk.
当我尽⼒去保证这篇⽂章中的所有内容及⽰例都是正确且⽆bug的，我并不对任何不愉快的事负责如程序崩溃，数据丢失及任何损害，当你⽤这篇⽂章中的信息及代码，我尽可能保证所有的bug都被调试通过并且内容都是准确的，简⽽⾔之，要有些常识并且⾃在⾃⼰的盘⾥使⽤它。

Mike's Version of 3D Graphics Theory
迈克关于3D图形理论的看法
When I started 3D graphics in WPF (back when it was still called Avalon), I had no idea what I was doing. I didn't have a clue what the significance was of a mesh, triangle index, or normal. This was the most painful part about learning 3D modeling, because without a minimal understanding of these things, nothing will show up correctly in WPF (or you'll just get lucky). In short, all you really need to know is what a mesh is and what it is composed of .
当我开始⽤WPF进⾏3D图形编程时，我不知道我正在做什么，对于⽹格（mesh），三⾓形索引（triangle index）或法线（normal）的复杂我毫⽆头绪。

对于3D建模这是最痛苦的，因为关于这些东西没有⼀种简短易懂的解释，在WPF⾥没有什么可以突然展现出来，简⽽⾔之，所有你所需要知道的是：什么是mesh及它是由什么组成的。

What is a mesh?
什么是mesh？
A mesh is basically a representation of a surface. The mesh represents the surface through a system of points and lines. The points describe the high and low areas of the surface, and the lines connect the points to establish how you get from one point to the next.
⼀个⽹,基本上是⼀个代表性的表⾯. ⽹通过系统的点线代表⾯,点形容⾼与低的地区的地表, ⽽且线连接点,以建⽴你怎样从⼀个点到下.
At a minimum, a surface is a flat plane. A flat plane needs three points to define it. Thus, the simplest surface that can be described in a mesh is a single triangle. It turns out that meshes can only be described with triangles. That is because a triangle is the simplest, most granular way to define a surface. A large, complex surface obviously can't be accurately described by one triangle. Instead, it can be approximated by many smaller triangles. You could argue that you could use a rectangle to define a surface, but it's not as granular as a triangle. When you think about it, a rectangle can be broken into two triangles. Two triangles can much more accurately describe a surface than a single rectangle. Ok enough... the point is that a mesh represents a surface through many triangles.
A whole mesh is composed of:
Mesh Positions
Triangle indeces
Triangle normals
⾄少,⼀个表⾯是⼀个平⾯. 三点确定⼀个平⾯. 因此,最简单的表⾯上,可以说，⼀⽹是⼀个三⾓形. 这是因为⼀个三⾓形是最简单,最粒状地界定了表⾯. ⼤型复杂曲⾯显然不能准确地被⼀个三⾓形描述. 相反,它可通过许多较⼩的三⾓形进⾏组合. 你可以说你能够⽤⼀个长⽅形来确定⼀个⾯, 但它不是粒状作为⼀个三⾓形. 当你想想看,⼀个长⽅形,可分为两个三⾓形. 两个三⾓形可以更准确地描述⼀个表⾯⽐单⼀的长⽅形. ok... 问题是,⽹是⼀个通过许多三⾓形组成的表⾯.
整个⽹组成是:
•⽹位置
•三⾓⾏
•三⾓形法线
Mesh Positions
⽹格位置
A mesh position is the location of a single point on a surface. The more dense the points are, the more accurately the mesh describes the surface.
⼀⽹位置是⼀个表⾯上⼀个单点的位置. 点的密度越⼤,⽹越能更加准确地描述了表⾯.
Triangle Indeces
三⾓形索引
A triangle index is a mesh position that defines one of the three points of a triangle in the mesh. The mesh positions alone cannot describe the mesh triangles. After the positions have been added, you need to define what positions make up which triangles.
⼀个三⾓形指数是⼀个⽹格位置,确定了⽹格中⼀个三⾓形的3点中的⼀个点. 仅仅⽹位置不⾜以形容⽹格三⾓形. 位置加⼊后,你必须确定在什么位置上组成了哪些三⾓形.
In WPF, the order in which you add mesh positions is important. A position's index value in a mesh's position collection is used when adding triangle indeces. For example, let's say you have a surface composed of five positions {p0, p1, p2, p3, p4}. If you wanted to define a triangle from p1, p3, and p4, you would add triangle indeces with index values 1, 3, and 4. If the positions were added in a different order {p3, p4, p0, p2, p1} and you wanted a triangle made of the same positions, you would add triangle indeces with index values 4, 0, and 1.
在wpf中 , 添加⽹位置（mesh positions）的命令是⾮常重要的.当你添加三⾓形时需要⽤到⽹格位置集合中的⼀个位置索引值. 举例来说,你有⼀个由五个点( p0 , p1 , p2 , p3 , p4 )组成的⾯ . 如果你想通过p1 , p3 , p4确定⼀个三⾓形, 你会添加三⾓索引（triangle indeces）通过索引值1 , 3和4 . 如果这些位置通过不同的秩序( p3 , p4 , p0 , p2 , p1 )添加 ,你想要由⼀个相同位置组成的三⾓形, 你会放⼊三⾓索引（triangle indeces）与索引值4 , 0和1 .
The order in which you add triangle indeces is also important. When you define a triangle, you are basically defining the points in either a clockwise or counter-clockwise direction (depending on which side of the triangle you're on, of course). The reason this is important is because it affects which side of the triangle is visible. When I say "side", I don't mean which of the three triangle sides, but which side of the plane.
添加三⾓索引（triangle indeces）的命令也是很重要的. 当你定义⼀个三⾓形, 你基本上确定了它的点,要么以顺时针或逆时针⽅向(取决于你看到的三⾓形的哪⼀⽅) .这是很重要的,因为它影响到的三⾓形哪⼀边是可见的. 当我说"side" ,我不是指三⾓形的哪⼀边,⽽是指⼀个平⾯的哪⼀⾯。

Let's say you're looking straight ahead at the surface of a triangle. If you define its indeces in a clockwise direction, the side you are looking at will be invisible and the opposite side will be visible. If you define its indeces in a counter-clockwise direction, the side you are looking at will be visible and the opposite side will be invisible. You can use the "right hand rule" to remember this. Take your right hand and make a "thumbs up" sign. The direction your fingers curl is counter-clockwise and your thumb points up (or out) in the direction the surface would be visible.
话⼜说回来,你直接看到的是⼀个三⾓形的表⾯. 如果你以顺时针⽅向确定索引, 你正在看的那⼀⾯将要是不可见的⽽它的另⼀⾯是可见的. 如果你以逆时针⽅向确定索引, 站在你的位置将会看得见,对⽅将看不见. 你可以⽤"右⼿定则"记住这⼀点. 以右⼿作出⼀个"⼤拇指"的⼿势.⼿指卷曲⽅向是时针⽅向，拇指⽅向的表⾯是可见的.
Exactly why a right-hand-rule applies to index ordering is beyond me. My best guess is that WPF doesn't think it is necessary or efficient to render both sides of the triangle, so you need to pick one of them.
正是右⼿规则适⽤于指数排序令⼈费解. 我最好的猜测是wpf并不认为有必要或有效率,使双⽅的三⾓形所以你需要选择其中之⼀.
Triangle Normals
三⾓形的法线
After defining positions and triangle indeces, you need to add normals to each position. While the direction in which you add triangle indeces determines which side of the triangle is visible, a normal is used by WPF to know how the surface should be lit by a light source.
在界定位置和三⾓索引 ,你还要为每个位置加⼊法线. ⽽⽅向是你放⼊三⾓索引时确定哪⼀侧的三⾓是可见的, wpf 通过使⽤法线知道表⾯是怎样被光源照射的.
A normal is a vector that is perpendicular to the surface of the triangle. The normal vector is computed as the "cross product" of two vectors that make up the side of the triangle. If you have a triangle defined by points A, B, and C, you could create the normal by multiplying A
B x AC, B
C x BA, or CB x CA. All three ways will result in the same normal. However, the right-hand rule still applies. AB x AC will result in a normal in the opposite direction from AC x AB.
法线是⼀个垂直于三⾓形表⾯的向量. 法线是三⾓形两边的两个差乘结果. 如果你有⼀个三⾓形，顶点为A , B和C , 你可以得到法线通过AB x AC, BC x BA, 或CB x CA. .三种⽅式得到在同样的法线.但是,右⼿定则仍然适⽤. AB x AC的结果与AC x AB相反.
At this point, my lack of knowledge of 3D theory begins to show, but in general you'll want your normals to point in the same direction as the visible side of your triangle surface.
在这⽅⾯看得出来,我缺乏三维理论知识, 但⼀般来说,你希望你的法线和三⾓形可见表⾯⽅向是⼀致的。

Each position in the mesh should have a normal assigned to it, and a position can only have one normal. You'll add normals to the mesh in the same order that you added the positions. In other words, the index values of the normals collection in the mesh corresponds to the index values of the positions collection.
⽹格中的各个位置应该被分配⼀个法线，并且⼀个位置只能有⼀个法线. 您可以⽤给位置加⼊法线的⽅法去给⽹格加⼊法线. 换句话说,在⽹格中法线索引值集合和位置值集合是⼀⼀对应的.
The more positions you have, the more normals you have. The more normals you have, the more pleasant the lighting and shading will be. In a mesh, a single point may be the index of more than one triangle. In this case, you may want to use multiple points with the same coordinates so that you can have multiple normals at that point. Take the corner of a cube, for example. The corner of a cube is the intersection of three different triangles on the cube. If you only used one position in the mesh to define the common index of those three triangles, you could only use one normal vector for that position. As a result, two of the triangles at that position won't be shaded as well as it could be. It would be better to define that
cube corner with three unique positions. Each of the three triangles would use their own unique points, and you could use three normals at that corner instead of just one.
你有愈多的位置，就有愈多的法线. 你有愈多的法线,你就更好的明暗效果. 在⼀个⽹格,单点可能是不⽌⼀个三⾓形的索引. 在这种情况下, 你可以使⽤多个具有同样座标的点,这样在那点上你可以有多条法线. 拿正⽅体的⼀个⾓打⽐⽅,. ⼀个⾓是⽴⽅体的三个不同的三⾓形相交的组成的. 如果你只⽤⽹格中的⼀个位置定义这三个三⾓形的法线,你只能⽤到那个位置的⼀个法线向量.结果是，三个三⾓形中的两个将不会想它应该的那样有阴影,⽤三个独⽴的位置去定义⽴⽅体的⾓会更好.三个三⾓形中的每个会⽤它⾃⼰单独的点, 并且你可以在那个⾓上⽤三个法线⽽不只是⼀个.。