Box2D c ++围绕点旋转

Question

但是，我也想让精灵的旋转反映出b2体的旋转。但是，在我旋转精灵之后，我用它来正确地将它们与b2体位置对齐的偏移不再准确。

void CRoom::RotateGun(const SDL_Event &event)
{
    glm::vec2 mousePosition = sdl::GetMousePosition(event.motion);
    glm::vec2 delta = mousePosition - GUN_POSITION;
    float angle = atan2f(delta.y, delta.x);
    m_gun->GetBody()->SetTransform(m_gun->GetPosition(), angle);
}

image1

Answer 1

Use the matrix multiply.

Using the normal conventions, the transform is

 move(-width/2, -height/2) * rotate(angle) * move(width/2 height/2) *move(x, y)

Sometimes you will have to reverse the order.