lookAt that returns camera matrix instead of view matrix-CodePudding

I can generate the camera matrix as follows:

void lookAt(vec3 center) {
    vec3 f = normalize(center - this->eye);
    vec3 u(0, 1, 0);
    vec3 r = normalize(cross(f, u));
    u = cross(r, f);
    this->cameraMatrix = inverse(mat4(
            r.x, u.x, -f.x, 0,
            r.y, u.y, -f.y, 0,
            r.z, u.z, -f.z, 0,
            -dot(r, this->eye), -dot(u, this->eye), dot(f, this->eye), 1
    ));
    // update MVP
}

I then update my MVP matrix, using V = inverse(this->cameraMatrix). I want to store the camera matrix so I can do easy translations/rotations.

The above code works but isn't very efficient. I don't understand the maths enough, but I was hoping for a way to directly calculate the cameraMatrix, given f, u, r, this->eye.

Thanks

CodePudding user response：

Given the camera position (eye), the camera target (center), and the up vector (upVector), the matrix that defines the position and orientation of the orientation can be calculated in a right-handed system where the x-axis is to the left, the y-axis is the up-vector, and the z-axis is points in the opposite direction of the line of sight, as follows:

glm::vec3 zAxis = glm::normalize(eye - center);
glm::vec3 xAxis = glm::normalize(glm::cross(upVector, zAxis));
glm::vec3 yAxis = glm::cross(zAxis, xAxis);
glm::mat4 cameraMatrix = glm::mat4(
    glm::vec4(xAxis, 0),
    glm::vec4(yAxis, 0),
    glm::vec4(zAxis, 0),
    glm::vec4(eye, 1.0f));

This is a matrix that transforms from view space to world space.