/// Returns signed 2 theta (signed scattering angle w.r.t. to beam direction).
double
DetectorInfo::signedTwoTheta(const std::pair<size_t, size_t> &index) const {
if (isMonitor(index))
throw std::logic_error(
"Two theta (scattering angle) is not defined for monitors.");
const auto samplePos = samplePosition();
const auto beamLine = samplePos - sourcePosition();
if (beamLine.nullVector()) {
throw Kernel::Exception::InstrumentDefinitionError(
"Source and sample are at same position!");
}
// Get the axis defining the sign
const auto &instrumentUpAxis =
m_instrument->getReferenceFrame()->vecThetaSign();
const auto sampleDetVec = position(index) - samplePos;
double angle = sampleDetVec.angle(beamLine);
const auto cross = beamLine.cross_prod(sampleDetVec);
const auto normToSurface = beamLine.cross_prod(instrumentUpAxis);
if (normToSurface.scalar_prod(cross) < 0) {
angle *= -1;
}
return angle;
}
void Shape::sampleDirect(DirectSamplingRecord &dRec,
const Point2 &sample) const {
/* Piggyback on sampleArea() */
samplePosition(dRec, sample);
dRec.d = dRec.p - dRec.ref;
Float distSquared = dRec.d.lengthSquared();
dRec.dist = std::sqrt(distSquared);
dRec.d /= dRec.dist;
Float dp = absDot(dRec.d, dRec.n);
dRec.pdf *= dp != 0 ? (distSquared / dp) : 0.0f;
dRec.measure = ESolidAngle;
}
/// Returns 2 theta (scattering angle w.r.t. to beam direction).
double DetectorInfo::twoTheta(const std::pair<size_t, size_t> &index) const {
if (isMonitor(index))
throw std::logic_error(
"Two theta (scattering angle) is not defined for monitors.");
const auto samplePos = samplePosition();
const auto beamLine = samplePos - sourcePosition();
if (beamLine.nullVector()) {
throw Kernel::Exception::InstrumentDefinitionError(
"Source and sample are at same position!");
}
const auto sampleDetVec = position(index) - samplePos;
return sampleDetVec.angle(beamLine);
}
bool Cube::sampleDirect(uint32 /*threadIndex*/, const Vec3f &p, PathSampleGenerator &sampler, LightSample &sample) const
{
PositionSample point;
samplePosition(sampler, point);
Vec3f L = point.p - p;
float rSq = L.lengthSq();
sample.dist = std::sqrt(rSq);
sample.d = L/sample.dist;
float cosTheta = -(point.Ng.dot(sample.d));
if (cosTheta <= 0.0f)
return false;
sample.pdf = rSq/(cosTheta*_area);
return true;
}
/** Returns L2 (distance from sample to spectrum).
*
* For monitors this is defined such that L1+L2 = source-detector distance,
* i.e., for a monitor in the beamline between source and sample L2 is negative.
*/
double DetectorInfo::l2(const std::pair<size_t, size_t> &index) const {
if (!isMonitor(index))
return position(index).distance(samplePosition());
else
return position(index).distance(sourcePosition()) - l1();
}
Vertex Triangle::sampleVertex(){
glm::vec3 position = samplePosition();
glm::vec3 normal = computeNormal(position);
return Vertex(position, normal);
}
