Method Slerp

implot3d.cpp:3711–3741

bool ImPlot3DQuat::operator!=(const ImPlot3DQuat& rhs) const { return !(*this == rhs); }

ImPlot3DQuat ImPlot3DQuat::Slerp(const ImPlot3DQuat& q1, const ImPlot3DQuat& q2, double t) {
    // Clamp t to [0, 1]
    t = ImClamp(t, 0.0, 1.0);

    // Compute the dot product (cosine of the angle between quaternions)
    double dot = q1.x * q2.x + q1.y * q2.y + q1.z * q2.z + q1.w * q2.w;

    // If the dot product is negative, negate one quaternion to take the shorter path
    ImPlot3DQuat q2_ = q2;
    if (dot < 0.0) {
        q2_ = ImPlot3DQuat(-q2.x, -q2.y, -q2.z, -q2.w);
        dot = -dot;
    }

    // If the quaternions are very close, use linear interpolation to avoid numerical instability
    if (dot > 0.9995) {
        return ImPlot3DQuat(q1.x + t * (q2_.x - q1.x), q1.y + t * (q2_.y - q1.y), q1.z + t * (q2_.z - q1.z), q1.w + t * (q2_.w - q1.w)).Normalized();
    }

    // Compute the angle and the interpolation factors
    double theta_0 = acos(dot);        // Angle between input quaternions
    double theta = theta_0 * t;        // Interpolated angle
    double sin_theta = sin(theta);     // Sine of interpolated angle
    double sin_theta_0 = sin(theta_0); // Sine of original angle

    double s1 = cos(theta) - dot * sin_theta / sin_theta_0;
    double s2 = sin_theta / sin_theta_0;

    // Interpolate and return the result
    return ImPlot3DQuat(s1 * q1.x + s2 * q2_.x, s1 * q1.y + s2 * q2_.y, s1 * q1.z + s2 * q2_.z, s1 * q1.w + s2 * q2_.w);
}

double ImPlot3DQuat::Dot(const ImPlot3DQuat& rhs) const { return x * rhs.x + y * rhs.y + z * rhs.z + w * rhs.w; }