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c++vectoreigenquaternions

Eigen slerp resulting in a Read Access Violation (C++/OpenGL)

I'm calling slerp() from the Eigen libary as follows:

Eigen::MatrixXf Rtime = (Eigen::Quaternionf::Identity().slerp(timer, quarts[i])).toRotationMatrix();

where timer is a float and quarts is declared as

std::vector<Eigen::Quaternionf> quarts;

This call to slerp only causes a Read Access Violation sometimes (about 50% of the time) , which confuses me.

Looking at the stack frame, Stack Frame I can see that the code reaches Eigen::internal::pload until it breaks.

Generally I'd think that my indices are incorrect but it crashes even when i = 0 and quarts.size() = 1. I declare the only quaternion in the vector:

Eigen::Matrix3f rotMatrix;
    rotMatrix = U * V;
    Eigen::Quaternionf temp;
    temp = rotMatrix;
    quarts.push_back(temp);

where U and V come from a computation of Singular Value Decomposition, so maybe there's something wrong with the way I declare the quaternion? Or storing it in a vector in some way affects it? I'm not sure.

Solution

  • The problem is that Quaternionf requires 16 bytes alignment that is not guaranteed by std::vector. More details there. The solutions are either to use an aligned allocator, e.g.:

    std::vector<Quaternionf,Eigen::aligned_allocator<Quaternionf>> quats;

    or to use non-aligned quaternions within the vector:

    std::vector<Quaternion<float,Eigen::DontAlign>> quats;