transform.h

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#pragma once
 
#include <liboscar/maths/quaternion.h>
#include <liboscar/maths/vector.h>
 
#include <ostream>
 
namespace osc
{
    // packaged-up SQT transform (scale -> rotate -> translate)
    struct Transform final {
 
        constexpr Transform with_translation(const Vector3& new_translation) const
        {
            return Transform{.scale = scale, .rotation = rotation, .translation = new_translation};
        }
 
        constexpr Transform with_rotation(const Quaternion& new_rotation) const
        {
            return Transform{.scale = scale, .rotation = new_rotation, .translation = translation};
        }
 
        constexpr Transform with_scale(const Vector3& new_scale) const
        {
            return Transform{.scale = new_scale, .rotation = rotation, .translation = translation};
        }
 
        constexpr Transform with_scale(float new_scale) const
        {
            return Transform{.scale = Vector3{new_scale}, .rotation = rotation, .translation = translation};
        }
 
        friend bool operator==(const Transform&, const Transform&) = default;
 
        Vector3 scale{1.0f};
        Quaternion rotation{};
        Vector3 translation{};
    };
 
    // applies the transform to a point vector (equivalent to `transform_point`)
    constexpr Vector3 operator*(const Transform& transform, Vector3 point)
    {
        point *= transform.scale;
        point  = transform.rotation * point;
        point += transform.translation;
        return point;
    }
 
    template<typename T>
    constexpr T identity();
 
    template<>
    constexpr Transform identity<Transform>()
    {
        return Transform{};
    }
 
    inline std::ostream& operator<<(std::ostream& out, const Transform& transform)
    {
        return out << "Transform(translation = " << transform.translation << ", rotation = " << transform.rotation << ", scale = " << transform.scale << ')';
    }
}