如何向相机方向移动，OpenGL，c ++

Question

我正在开始一个3D场景，我正在研究相机的运动，或者实体四处走动，但我似乎无法得到它朝着它面向的方向移动。

有没有人对我如何开始向相机方向移动有任何指导？但是我只希望实体沿着x和z轴移动，就像它在地板上一样，y轴现在将被忽略。如果有人能告诉我涉及什么数学，那就非常感激。

Camera::Camera(Vector3 * eye, Vector3 * center, Vector3 * up) {
    this->eye = eye;
    this->center = center;
    this->up = up;
}

Camera::Vector3 * getEye() { return eye; }
Camera::Vector3 * getCenter() { return center; }
Camera::Vector3 * getUp() { return up; }



camera = new Camera(new Vector3(5.0f, 3.0f, 5.0f), 
    new Vector3(0.0f, 0.0f, 0.0f), 
    new Vector3(0.0f, 1.0f, 0.0f));


gluLookAt(camera->eye->getX(), camera->eye->getY(), camera->eye->getZ(),
            camera->center->getX(), camera->center->getY(), camera->center->getZ(),
            camera->up->getX(), camera->up->getY(), camera->up->getZ());//camera

Answer 1

您还可以直接从视图矩阵中提取视图矢量 - 在渲染场景之前应用的视图矩阵。

OpenGL模型/视图矩阵如下所示：

|lx,ux,vx,px|     -- lx,ly,lz is your left-vector
|ly,uy,vy,py|     -- ux,uy,uz is your up-vector
|lz,uz,vz,pz|     -- vx,vy,vz is your view-vector
|0 ,0 ,0 ,1 |     -- px,py,pz is your translation 

通过获取：

简单地提取视图向量

vx = matrix[2]; 
vy = matrix[6]; 
vz = matrix[10];

我通常在旋转相机后执行此操作，以便应用移动。在继续使用它们进行数学运算之前，将这些向量标准化是一种很好的做法。

Answer 2

背后的数学很简单。首先需要2个vec3（一个用于相机位置，一个用于外观位置）

我假设你的向上矢量是（0,1,0）。所以计算应该是这样的：

vec3 lookatPosition;
vec3 cameraPosition;
vec3 upVector(0,1,0);
float movementSpeed;


vec3 forwardVector = lookatPosition - cameraPosition;

//You can generate like that if you don't have operator overload
//forwardVector.x = lookatPosition.x - cameraPosition.x;
//forwardVector.y = lookatPosition.y - cameraPosition.y;
//forwardVector.z = lookatPosition.z - cameraPosition.z;

forwardVector.normalise() // normalise your vector



//moving forward :
cameraPosition += forwardVector * movementSpeed;
lookatPosition += forwardVector * movementSpeed;

//Again you can do the operation like that if you don't have operator overloading
//cameraPosition.x += forwardVector.x * movementSpeed;
//cameraPosition.y += forwardVector.y * movementSpeed;
//cameraPosition.z += forwardVector.z * movementSpeed;

//moving backward :
cameraPosition -= forwardVector * movementSpeed;
lookatPosition -= forwardVector * movementSpeed;

//moving left :
vec3 leftVector = Crossproduct(upVector,forwardVector);
cameraPosition += leftVector * movementSpeed;
lookatPosition += leftVector * movementSpeed;


//moving right :
vec3 rightVector = Crossproduct(forwardVector,upVector);
cameraPosition += rightVector * movementSpeed;
lookatPosition += rightVector * movementSpeed;

注意：数据类型和函数名称不是内置的，您可以实现自己的数据类型或使用glm作为向量。