关于AS3里的Matrix3D中的appendXXX和prependXXX

浏览数：26 / 时间：2015年06月11日

最近在看3D相关的一些基础，因为搞as3这么多年了，决定3D基础这块还是从AS3入手，3D游戏开发这块从U3D入手，扯远了，研究Matrix3D类时发现了矩阵处理转换时的一些方法均分为appendXXX和prependXXX两种，帮助文档中的解释是后置和前置的区别，搞不清楚，所以决定花点时间弄一下这个东西。

直接上代码，最后一行注释是前四行代码的执行结果：

 1 var m:Matrix3D = new Matrix3D();
 2 m.appendRotation(45, Vector3D.X_AXIS);
 3 m.appendTranslation(10, 20, 30);
 4 trace(m.decompose());
 5 //Vector3D(10, 20, 30),Vector3D(0.7853981852531433, 0, 0),Vector3D(1, 1, 1)
 6 
 7 var m:Matrix3D = new Matrix3D();
 8 m.appendTranslation(10, 20, 30);
 9 m.appendRotation(45, Vector3D.X_AXIS);
10 trace(m.decompose());
11 //Vector3D(10, -7.071067810058594, 35.35533905029297),Vector3D(0.7853981852531433, 0, 0),Vector3D(1, 1, 1)
12 
13 var m:Matrix3D = new Matrix3D();
14 m.prependRotation(45, Vector3D.X_AXIS);
15 m.prependTranslation(10, 20, 30);
16 trace(m.decompose());
17 //Vector3D(10, -7.071067810058594, 35.35533905029297),Vector3D(0.7853981852531433, 0, 0),Vector3D(1, 1, 1)
18 
19 var m:Matrix3D = new Matrix3D();
20 m.prependTranslation(10, 20, 30);
21 m.prependRotation(45, Vector3D.X_AXIS);
22 trace(m.decompose());
23 //Vector3D(10, 20, 30),Vector3D(0.7853981852531433, 0, 0),Vector3D(1, 1, 1)

上面的示例可以看出两者之间的差距是运算顺序不同，prependXXX的运算顺序是反过来的，好吧，我们再看一个示例：

 1 var m:Matrix3D = new Matrix3D();
 2 m.appendRotation(45, Vector3D.X_AXIS);
 3 m.appendTranslation(10, 15, 20);
 4 m.appendTranslation(10, 15, 20);
 5 m.appendRotation(45, Vector3D.Y_AXIS);
 6 m.appendTranslation(10, 15, 20);
 7 m.appendTranslation(10, 20, 30);
 8 m.appendRotation(45, Vector3D.Z_AXIS);
 9 trace(m.decompose());
10 //Vector3D(-1.8198051452636719, 90.10408020019531, 64.14213562011719),Vector3D(0.7853981852531433, 0.7853982448577881, 0.7853981852531433),Vector3D(1, 1, 1)
11 m.appendTranslation(10, 20, 30);
12 trace(m.decompose());
13 //Vector3D(8.180194854736328, 110.10408020019531, 94.14213562011719),Vector3D(0.7853981852531433, 0.7853982448577881, 0.7853981852531433),Vector3D(1, 1, 1)
14 
15 var m:Matrix3D = new Matrix3D();
16 m.appendRotation(45, Vector3D.X_AXIS);
17 m.appendTranslation(10, 15, 20);
18 m.appendTranslation(10, 15, 20);
19 m.appendRotation(45, Vector3D.Y_AXIS);
20 m.appendTranslation(10, 15, 20);
21 m.appendTranslation(10, 20, 30);
22 m.appendRotation(45, Vector3D.Z_AXIS);
23 trace(m.decompose());
24 //Vector3D(-1.8198051452636719, 90.10408020019531, 64.14213562011719),Vector3D(0.7853981852531433, 0.7853982448577881, 0.7853981852531433),Vector3D(1, 1, 1)
25 m.prependTranslation(10, 20, 30);
26 trace(m.decompose());
27 //Vector3D(25.857860565185547, 107.78174591064453, 82.0710678100586),Vector3D(0.7853981852531433, 0.7853982448577881, 0.7853981852531433),Vector3D(1, 1, 1)