GPUDisplayQuaternion.cxx

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
 
 
#include "GPUDisplay.h"
 
#include <cmath>
using namespace o2::gpu;
 
void GPUDisplay::createQuaternionFromMatrix(float* v, const float* mat)
{
  if (mat[0] > mat[5] && mat[0] > mat[10]) {
    const float S = sqrt(std::max(0.f, 1.0f + mat[0] - mat[5] - mat[10])) * 2;
    v[0] = 0.25f * S;
    v[1] = (mat[4] + mat[1]) / S;
    v[2] = (mat[2] + mat[8]) / S;
    v[3] = (mat[9] - mat[6]) / S;
  } else if (mat[5] > mat[10]) {
    const float S = sqrt(std::max(0.f, 1.0f + mat[5] - mat[0] - mat[10])) * 2;
    v[1] = 0.25f * S;
    v[0] = (mat[4] + mat[1]) / S;
    v[2] = (mat[9] + mat[6]) / S;
    v[3] = (mat[2] - mat[8]) / S;
  } else {
    float S = sqrt(std::max(0.f, 1.0f + mat[10] - mat[0] - mat[5])) * 2;
    v[2] = 0.25f * S;
    if (fabsf(S) < 0.001f) {
      S = 1;
    }
    v[0] = (mat[2] + mat[8]) / S;
    v[1] = (mat[9] + mat[6]) / S;
    v[3] = (mat[4] - mat[1]) / S;
  }
  if (v[0] * v[0] + v[1] * v[1] + v[2] * v[2] + v[3] * v[3] < 0.0001f) {
    v[3] = 1;
  }
}