Accessing quaternion identity is currently not elegant

[Robert42]

There's no easy way of getting an identity for quaternions

In the experimental headers, there's a function

quat_identity<T, Q>()

As quad_identity accepts no function arguments, you have to pass the template arguments T and Q explicitely resulting in calls like

glm::quat_identity<glm::quat::value_type, glm::highp>()

which in my opinion reveals more knowledge of glm implementation details than necessary.

My personal preference

My personally prefered would be to return to the old way of calling

glm::quat::IDENTITY

or something comparable like using static class functions for easy initialization in general:

glm::quat::identitfy()
glm::vec3::x_axis() // Returns glm::vec3(1, 0, 0)

But for some reason, this was removed, so I assume that's not an option. So here are two other suggestions:

Alternative suggestion1: initialization template class

A template class providing static functions with interesting values.
Something comparable to std::numeric_limits ;)

This would make typical values quickly accessible

glm::init<glm::quat>::identity()
glm::init<glm::vec3>::x_axis() // Returns glm::vec3(1, 0, 0)

Here the user has to provide only the quat type he wants to use as template argument

Alternative suggestion 2:

A function only accepting the whole quat type as only argument

template<typename quat_type>
inline quat_type quat_identity()
{
  quat_type q;
  q.x = q.y = q.z = typename quat_type::value_type(0);
  q.w = typename quat_type::value_type(1);
  return q;
}

This implemetation could be used like this:

glm::quat_identity<glm::quat>()

Here the user also has to provide only the quat type he wants to use as template argument

[gurki]

/sign

I support your static class accessor proposal, which I implement myself for every project anyways. It's elegant and non-instrusive.

[Groovounet]

The idea is pretty interesting and could be generalized to others types.

Thanks!

[Groovounet]

Based on your ideas I found an implementation that makes the function to look like this:
glm::quat const Q = glm::identity<glm::quat>(); glm::mat4 const M = glm::identity<glm::mat4x4>();

I should be able to extend this to glm::x_axis<glm::vec3>().

[Groovounet]

This issue is fixed in master branch for GLM 0.9.9.1 release.

Thanks for contributing,
Christophe