CODEWITHSUNDEEP
openglrotationquaternionsglm-math
Kakalokia
Kakalokia

Reputation: 3191

Rotating an object with quaternion

I have a question in regards to using quaternions for the rotation of my graphics object.

I have a Transform class which has the following constructor with default parameters:

Transform(const glm::vec3& pos = glm::vec3(0.0), const glm::quat& rot = glm::quat(1.0, 0.0, 0.0, 0.0),
    const glm::vec3& scale = glm::vec3(1.0))
{
    m_pos = pos;
    m_rot = rot;
    m_scale = scale;
}

In my Transform class calculate the MVP as follows:

glm::mat4 Transform::GetModelMatrix() const
{
    glm::mat4 translate = glm::translate(glm::mat4(1.0), m_pos);
    glm::mat4 rotate = glm::mat4_cast(m_rot);
    glm::mat4 scale = glm::scale(glm::mat4(1.0), m_scale);

    return translate * rotate * scale;
}

The issue I'm facing is that when I use const glm::quat& rot = glm::quat(1.0, 0.0, 0.0, 0.0) my object appears normal on screen. The following image shows it: enter image description here

However if I try to use for example const glm::quat& rot = glm::quat(glm::radians(90.0f), 0.0, 1.0, 0.0) (rotating on y axis by 90 degrees) my object appears as if it has been scaled. The following image shows it: enter image description here

I can't figure out what is causing it to become like this when I try to rotate it. Am I missing something important?

If it's of any relevance, the following is how I calculate my view matrix:

glm::mat4 Camera::GetView() const
{
    glm::mat4 view = glm::lookAt(m_pos, m_pos + m_forward, m_up);

    return view;
}

Upvotes: 1

Views: 3030

Answers (1)

MalaKa
MalaKa

Reputation: 3794

AFAIK you can init a glm::quat using: 

glm::vec3 angles(degToRad(rotx), degToRad(roty), degToRad(rotz));
glm::quat rotation(angles);

Where rotx, roty, rotz are the rotation angles around x, y and z axis and degToRad converts angles to radians. Therefore for your case:

glm::vec3 angles(degToRad(0), degToRad(90), degToRad(0));
glm::quat rotation(angles);

Regards

Upvotes: 1

Related Questions