如何相对于观看方向在地形中四处移动

Question

我想相对于当前查看方向在地形（m_mouseMovement中的delta x，delta y）中向左/向右，向前/向后移动。以下代码适用于缩放（鼠标滚轮）。但是，只有在观看方向恰好沿x轴方向移动时，运动才起作用：

Vector3D m_position;
Vector2D m_mouseMovement; // delta x,y amount the mouse was moved on the screen
int m_mouseWheelSteps;

QVector3D direction(...);
QVector3D right(...);
QVector3D up = QVector3D::crossProduct(right, direction);

m_position += m_mouseWheelSteps * direction; // zoom in and out; ok

// m_position += Vector3D(m_mouseMovement.x*right.x, 0, m_mouseMovement.z*right.z); // does not work properly; it always moves along the x/z axis

QMatrix4x4 modelMatrix;
//modelMatrix.scale, translate, etc. the terrain

QMatrix4x4 viewMatrix;
viewMatrix.lookAt(m_position, m_position+direction, up);

QMatrix4x4 mvMatrix = viewMatrix * modelMatrix;

QMatrix4x4 projectionMatrix;
projectionMatrix.perspective(...);

QMatrix4x4 mvpMatrix = projectionMatrix*mvMatrix;

我无法理解如何使它工作，从而使运动独立于观看方向？

Answer 1

简单的解决方案：

m_position += m_mouseMovement.x*Vector3D(right.x, 0, right.z);
//m_position += m_mouseMovement.y*Vector3D(up.x, 0, up.z);
m_position += m_mouseMovement.z*Vector3D(direction.x, 0, direction.z);