// Copyright CERN and copyright holders of ALICE O2. This software is

// distributed under the terms of the GNU General Public License v3 (GPL

// Version 3), copied verbatim in the file "COPYING".

//

// See http://alice-o2.web.cern.ch/license for full licensing information.

//

// 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.

/// \file Ray.cxx

/// \brief Implementation of ray between start-end points for material budget estimate

#include "DetectorsBase/Ray.h"

#include "GPUCommonMath.h"

using namespace o2::base;

using namespace o2::gpu;

//______________________________________________________

GPUd() int Ray::crossLayer(const MatLayerCyl& lr)

{

// Calculate parameters t of intersection with cyl.layer

// Calculated as solution of equation for ray crossing with circles of r (rmin and rmax)

// t^2*mDistXY2 +- sqrt( mXDxPlusYDy^2 - mDistXY2*(mR02 - r^2) )

// Region of valid t is 0:1.

// Straigh line may have 2 crossings with cyl. layer

float detMax = mXDxPlusYDy2 - mDistXY2 * (mR02 - lr.getRMax2());

if (detMax < 0) {

return 0; // does not reach outer R, hence inner also

}

float detMaxRed = CAMath::Sqrt(detMax) * mDistXY2i;

float tCross0Max = mXDxPlusYDyRed + detMaxRed; // largest possible t

if (tCross0Max < 0) { // max t is outside of the limiting point -> other t's also

return 0;

}

float tCross0Min = mXDxPlusYDyRed - detMaxRed; // smallest possible t

if (tCross0Min > 1.f) { // min t is outside of the limiting point -> other t's also

return 0;

}

float detMin = mXDxPlusYDy2 - mDistXY2 * (mR02 - lr.getRMin2());

if (detMin < 0) { // does not reach inner R -> just 1 tangential crossing

mCrossParams1[0] = tCross0Min > 0.f ? tCross0Min : 0.f;

mCrossParams2[0] = tCross0Max < 1.f ? tCross0Max : 1.f;

return validateZRange(mCrossParams1[0], mCrossParams2[0], lr);

}

int nCross = 0;

float detMinRed = CAMath::Sqrt(detMin) * mDistXY2i;

float tCross1Max = mXDxPlusYDyRed + detMinRed;

float tCross1Min = mXDxPlusYDyRed - detMinRed;

if (tCross1Max < 1.f) {

mCrossParams1[0] = tCross0Max < 1.f ? tCross0Max : 1.f;

mCrossParams2[0] = tCross1Max > 0.f ? tCross1Max : 0.f;

if (validateZRange(mCrossParams1[nCross], mCrossParams2[nCross], lr)) {

nCross++;

}

}

if (tCross1Min > -0.f) {

mCrossParams1[nCross] = tCross1Min < 1.f ? tCross1Min : 1.f;

mCrossParams2[nCross] = tCross0Min > 0.f ? tCross0Min : 0.f;

if (validateZRange(mCrossParams1[nCross], mCrossParams2[nCross], lr)) {

nCross++;

}

}

return nCross;

}