C++ OpenGL how to get rotations x,y,z from quaterion - c++

Question

I have been handling object rotations in my engine by storing object`s x,y and z rotation and then when I am about to render, I was creating the transformation matrix like this.
// entity.getRotation() returns a glm::vec3 where I use these
//values to rotate the object.
glm::mat4 model;
model = glm::translate(model, entity.getPosition());
model = glm::rotate(model, glm::radians(entity.getRotation().x), glm::vec3(1.0f, 0.0f, 0.0f));
model = glm::rotate(model, glm::radians(entity.getRotation().y), glm::vec3(0.0f, 1.0f, 0.0f));
model = glm::rotate(model, glm::radians(entity.getRotation().z), glm::vec3(0.0f, 0.0f, 1.0f));
model = glm::scale(model, glm::vec3(entity.getScale(), entity.getScale(), entity.getScale()));
Now, I implemented an AntTweakBar GUI into my engine where there is an option to be able to rotate objects on the GUI. I am currently trying to make it possible to rotate the objects in GUI and see the resulting rotations in the engine. The problem is that GUI works with quaternions while in my engine object rotation is stored as 3 floats of x,y,z rotation amounts.
My question is, how can I take the quaternion and turn it into x, y, z rotations so that I can use my above mention method to create the transformation matrix?
I found this method in glm
glm::eulerAngles(glm::quat(q[0], q[1], q[2], q[3]));
but upon looking at returned vec3, it does not seem like what I am looking for. I believe eulerAngles returns pitch, yaw, and roll which behaves incorrectly when I try to use these values to create my Transformation matrix.
Edit:
I found my mistake. It turned out that my old solution was fine(Although as someone pointed out in comments using quats might be faster). The problem was in my conversion from float array representation of quat(float array representation for AntTweakBar) to angles. It seems like AntTweakBar stores the x,y,z,w components in quat in a different order in the float array. The correct order in the float array is y,z,w,x but I have no clue why this is.

Answer 1

With GLM there are a couple of options, one that you have already mentioned, however make sure that your measure of angles are consistent. If you are using and relying on radians most of GLM's library methods past a specific version now expects all angles that are being passed into their rotation functions in radians however according to their docs when working with quaternions and using glm::eulerAngles(); it returns the angles pitch as X, yaw as Y, and roll as Z in degrees unless GLM_FORCE_RADIANS is defined.
Another alternative would be to use these two methods:
glm::mat4_cast
GLM_FUNC_DECL tmat4x4<T, P> glm::mat4_cast ( tquat< T, P > const & x )
Converts a quaternion to a 4 * 4 matrix.
See also GLM_GTC_quaternion Referenced by glm::toMat4().
glm::quat_cast
GLM_FUNC_DECL tquat<T, P> glm::quat_cast ( tmat4x4< T, P > const & x )
Converts a 4 * 4 matrix to a quaternion.
See also GLM_GTC_quaternion
If your GUI is using Quaternions you can retrieve that information and save it to a glm::quaternion then from there you can use one of these functions to convert it over to a 4x4 matrix. There are also 3x3 matrix-quat & quat-3x3 matrix versions of these conversion functions.