dirextx 如何计算mesh旋转后的包围盒的坐标

[hh23]

通过ComputeBoundingBox能够得到初始状态的min，max向量。但当z轴选择a度后min，max如何计算？

[IONPhantom]

先把模型进行坐标变换,每个顶点的位置就发生变化了,然后再用ComputeBoundingBox

[张赐]

一样的，mesh模型旋转或移动时，都是乘以旋转或位移矩阵
把这个矩阵同样乘以包围盒的坐标就可以了

[饭团大暴走]

[Quote=引用 1 楼 P_hantom 的回复:]
先把模型进行坐标变换,每个顶点的位置就发生变化了,然后再用ComputeBoundingBox
[/Quote]

或者

[Quote=引用 2 楼 zhangci226 的回复:]
一样的，mesh模型旋转或移动时，都是乘以旋转或位移矩阵
把这个矩阵同样乘以包围盒的坐标就可以了
[/Quote]

[ProgramRookie]

直接用变换阵乘包围盒是绝对错误的,自己画下就知道变换后模型很可能会不在包围盒内,应该先变换所得到的包围盒八个顶点,再从这8个顶点中计算出一个新的包围盒:
实例:
void SelfDefObj::CalculateBoundingBoxInWorld(){

D3DXVECTOR3 tmpMin, tmpMax;
D3DXVECTOR3 modelMin, modelMax;
this->m_worldAABB.GetDetails( tmpMax, tmpMin );
this->m_modelAABB.GetDetails( modelMax, modelMin );

//先获取平移量
tmpMin = tmpMax = D3DXVECTOR3( this->m_pMotelToWorld->_41, this->m_pMotelToWorld->_42, this->m_pMotelToWorld->_43 );

//再获取旋转缩放的变化
if( this->m_pMotelToWorld->_11 > 0.0f ){

tmpMin.x += this->m_pMotelToWorld->_11 * modelMin.x;
tmpMax.x += this->m_pMotelToWorld->_11 * modelMax.x;

}
else{

tmpMin.x += this->m_pMotelToWorld->_11 * modelMax.x;
tmpMax.x += this->m_pMotelToWorld->_11 * modelMin.x;

}

if( this->m_pMotelToWorld->_12 > 0.0f ){

tmpMin.y += this->m_pMotelToWorld->_12 * modelMin.y;
tmpMax.y += this->m_pMotelToWorld->_12 * modelMax.y;

}
else{

tmpMin.y += this->m_pMotelToWorld->_12 * modelMax.y;
tmpMax.y += this->m_pMotelToWorld->_12 * modelMin.y;

}

if( this->m_pMotelToWorld->_13 > 0.0f ){

tmpMin.z += this->m_pMotelToWorld->_13 * modelMin.z;
tmpMax.z += this->m_pMotelToWorld->_13 * modelMax.z;

}
else{

tmpMin.z += this->m_pMotelToWorld->_13 * modelMax.z;
tmpMax.z += this->m_pMotelToWorld->_13 * modelMin.z;

}

if( this->m_pMotelToWorld->_21 > 0.0f ){

tmpMin.x += this->m_pMotelToWorld->_21 * modelMin.x;
tmpMax.x += this->m_pMotelToWorld->_21 * modelMax.x;

}
else{

tmpMin.x += this->m_pMotelToWorld->_21 * modelMax.x;
tmpMax.x += this->m_pMotelToWorld->_21 * modelMin.x;

}

if( this->m_pMotelToWorld->_22 > 0.0f ){

tmpMin.y += this->m_pMotelToWorld->_22 * modelMin.y;
tmpMax.y += this->m_pMotelToWorld->_22 * modelMax.y;

}
else{

tmpMin.y += this->m_pMotelToWorld->_22 * modelMax.y;
tmpMax.y += this->m_pMotelToWorld->_22 * modelMin.y;

}

if( this->m_pMotelToWorld->_23 > 0.0f ){

tmpMin.z += this->m_pMotelToWorld->_23 * modelMin.z;
tmpMax.z += this->m_pMotelToWorld->_23 * modelMax.z;

}
else{

tmpMin.z += this->m_pMotelToWorld->_23 * modelMax.z;
tmpMax.z += this->m_pMotelToWorld->_23 * modelMin.z;

}

if( this->m_pMotelToWorld->_31 > 0.0f ){

tmpMin.x += this->m_pMotelToWorld->_31 * modelMin.x;
tmpMax.x += this->m_pMotelToWorld->_31 * modelMax.x;

}
else{

tmpMin.x += this->m_pMotelToWorld->_31 * modelMax.x;
tmpMax.x += this->m_pMotelToWorld->_31 * modelMin.x;

}

if( this->m_pMotelToWorld->_32 > 0.0f ){

tmpMin.y += this->m_pMotelToWorld->_32 * modelMin.y;
tmpMax.y += this->m_pMotelToWorld->_32 * modelMax.y;

}
else{

tmpMin.y += this->m_pMotelToWorld->_32 * modelMax.y;
tmpMax.y += this->m_pMotelToWorld->_32 * modelMin.y;

}

if( this->m_pMotelToWorld->_33 > 0.0f ){

tmpMin.z += this->m_pMotelToWorld->_33 * modelMin.z;
tmpMax.z += this->m_pMotelToWorld->_33 * modelMax.z;

}
else{

tmpMin.z += this->m_pMotelToWorld->_33 * modelMax.z;
tmpMax.z += this->m_pMotelToWorld->_33 * modelMin.z;

}

this->m_worldAABB.SetDetails( tmpMax, tmpMin );

}