message: use AMR testing volume
  working example
diff: @@ -161,8 +161,10 @@ OSPVolume createDummyAMRVolume()
  ospSetString(dummy, "voxelType", "float");
  //FileName fname("/mnt/ssd/test_data/test_amr");
  - FileName fname("/mnt/ssd/magnetic_amr");
  - parseRaw2AmrFile(fname, 4, 2);
  + //FileName fname("/mnt/ssd/magnetic_amr");
  + //parseRaw2AmrFile(fname, 4, 2);
  +
  + //std::vector<float> raw = ospray::testing::generateVoxels(256, 10);
  // ALOK: taken from ospray/master's AMRVolume::preCommit()
  // convert raw pointers in brickPtrs to OSPData in brickData
  @@ -213,13 +215,18 @@ int main(int argc, const char **argv)
  std::vector<OSPGeometryInstance> geometryInstances;
  // add in AMR volume
  - OSPVolume amrVolume = createDummyAMRVolume();
  + // OSPVolume amrVolume = createDummyAMRVolume();
  + OSPTestingVolume testData = ospTestingNewVolume("gravity_spheres_amr_volume");
  +
  + OSPVolume amrVolume = testData.volume;
  // create a volume instance container
  OSPVolumeInstance instance = ospNewVolumeInstance(amrVolume);
  + ospSetFloat(instance, "samplingRate", 10.f);
  // apply a transfer function to the instance
  - osp_vec2f amrValueRange = {valueRange.lower, valueRange.upper};
  + // osp_vec2f amrValueRange = {valueRange.lower, valueRange.upper};
  + osp_vec2f amrValueRange = testData.voxelRange;
  OSPTransferFunction tf = ospTestingNewTransferFunction(amrValueRange, "jet");
  ospSetObject(instance, "transferFunction", tf);
  ospCommit(instance);
  @@ -388,6 +395,8 @@ int main(int argc, const char **argv)
  }
  };
  + bounds = reinterpret_cast<box3f &>(testData.bounds);
  +
  // create a GLFW OSPRay window: this object will create and manage the OSPRay
  // frame buffer and camera directly
  auto glfwOSPRayWindow =
  