M3G内坐标系作用范围的混淆

M3G坐标系的混淆

mesh.translate(0.0f, 0.0f, 5.0f);

与

transform.postTranslate(0.0f, 0.0f, 5.0f);
mesh.setTransform(transform)

有什么区别？

答案：第一个是以mesh的父坐标系为基准，沿着父坐标系的Z轴平移

而第二个是以物体局部坐标系的Z轴移动，如果这个局部的Z轴经过了旋转，那就会沿着新的局部Z轴进行平移。

 

附M3G其它一些translate和rotate的规则说明：

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Transformable:
- postRotate(float angle, float ax, float ay, float az)
- translate(float tx, float ty, float tz)

 

Transform:
- postRotate(float angle, float ax, float ay, float az)
- postTranslate(float tx, float ty, float tz)

 

mesh.postRotate(3.0f, 1.0f, 0.0f, 0.0f);
When rotation is made directly on the transformable object the rotation will be made around the origo of the local co-ordinate system（局部坐标系的原点）.

 

transform.postRotate(3.0f, 1.0f, 0.0f, 0.0f);
mesh.setTransform(transform);
When the rotation is made using the transform class the object will rotate around its center(物体中心：取决于建模是规定的中心点，不一定是局部坐标系的原点).

 

mesh.translate(0.0f, 0.0f, 5.0f);
When the object is moved using methods in the transformable class the object is moved in the co-ordinate system of the parent node(父节点坐标系).

 

transform.postTranslate(0.0f, 0.0f, 5.0f);
mesh.setTransform(transform)
When the object is moved using the transform class the object is moved in the local co-ordinate system(局部坐标系).

----------------------------updated 2007-01-18--------------------------------

比如，我的

Camera cam;

Group camGroup;

在loadCamera时，

cam.translate(0.0f, 5.0f, 10.0f);

camGroup.addChild(cam);

world.addChild(camGroup);

那么在对相机进行旋转时，就需要操作camGroup，如果操作cam，则会导致translate的叠加效应

在平移时

如果camGroup.translate，则会导致camGroup在它父结点坐标系，也就是world的轴方向进行平移

如果要在相机局部坐标系下进行平移，则需要

cam.translate