从矢量的Direct3D旋转矩阵，反之亦然 [英] Direct3D Rotation Matrix from Vector and vice-versa

问题描述

我需要从一个方向向量
和一个旋转矩阵的方向向量计算一个旋转矩阵。

I need to compute a rotation matrix from a direction vector, and a direction vector from a rotation matrix.

向上方向应该对应于
forward是y，right是x;

The up direction should correspond to the z-axis, forward is y and right is x;

    D3DXMATRIX m; // the rotation matrix
    D3DXVECTOR3 v; // this is the direction vector wich is given
    D3DXVECTOR3 r; // resulting direction vector

    float len = D3DXVec3Length(&v); // length of the initial direction vector

    // compute matrix
    D3DXMatrixLookAtLH(&m, &v, &D3DXVECTOR3(0,0,0), &D3DXVECTOR3(0,0,1));

    // use the matrix on a vector { 0, len, 0 }
    D3DXVec3TransformCoord(&r, &D3DXVECTOR3(0,len,0), &m);

现在，向量 r 应该等于 v ，但它isnt。
我需要做什么才能得到我需要的结果？

Now, the vector r should be equal to v, but it isnt. What exactly do I have to do to get the results I need?

推荐答案

问题是有点混乱我。使用方向矢量，您可以定义无限旋转矩阵，这将使相机指向/查看该方向，除非您定义一些额外的约束。
我将根据你的代码假设你想要向上向量 Z ： - ）

The question is a bit confusing for me. Using a direction vector, you can define infinite rotation matrices that would make the camera point/look at that direction, unless you define some additional constraints. I will assume, based on your code, that you want the up vector to be Z :-)

首先，要小心：看起来你正在描述一个右手坐标系，但使用左手函数 D3DXMatrixLookAtLH 。
第二，这个函数的引用说：

In first place, be careful: it seems that you are describing a right-handed coordinate system, but using a left-handed function D3DXMatrixLookAtLH. In second place, reference for this function says that:

D3DXMATRIX* D3DXMatrixLookAtLH(
  _Inout_  D3DXMATRIX *pOut,
  _In_     const D3DXVECTOR3 *pEye,
  _In_     const D3DXVECTOR3 *pAt,
  _In_     const D3DXVECTOR3 *pUp
);

您正在创建一个查找矩阵，指定：

You are creating a look-at matrix specifying that:

• 相机位于 v 向量的末尾，


• 相机寻找 [0 0 0]

• The camera is located at the end of the v vector,
• Camera is looking towards [0 0 0]

您确定这是正确的，

第三，将旋转矩阵应用于缩放的 Y 基本向量 [0 length 0] 。如果你想要旋转的向量 v ，我想你应该应用它缩放的 X code> [len 0 0] 。

In third place, you are applying the rotation matrix to a scaled Y basis vector [0 length 0]. If you want the rotated vector to be v, I think you should apply it to the scaled X basis vector instead [len 0 0].

这篇关于从矢量的Direct3D旋转矩阵，反之亦然的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！