Resolve "Implement ce_MRICH"

Closes #12 (closed)

src/ce_MRICH.cpp

@@ -16,6 +16,11 @@ using namespace dd4hep::rec;
 typedef ROOT::Math::XYPoint Point;
 
 
+std::vector<Point> fillSquares(Point ref, double lside, double rmin, double rmax,
+                               double phmin = 0., double phmax = 2.*M_PI);
+void addModules(Volume &mother, xml::DetElement &detElem, Detector &desc, SensitiveDetector &sens);
+
+
 // create the detector
 static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetector sens)
 {
@@ -25,7 +30,6 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
 
     DetElement det(detName, detID);
     xml::Component dims = detElem.dimensions();
-    xml::Component mods = detElem.child(_Unicode(modules));
     xml::Component rads = detElem.child(_Unicode(radiator));
 
     auto RIn = dims.attr<double>(_Unicode(r_in));
@@ -34,18 +38,15 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
     auto PosZ = dims.z();
     auto InnerR = dims.attr<double>(_Unicode(inner_r));
 
-    auto mThick = mods.attr<double>(_Unicode(thickness));
-    auto mWidth = mods.attr<double>(_Unicode(width));
-    auto mGap = mods.attr<double>(_Unicode(gap));
-
-    auto envMat = desc.material(detElem.materialStr());
+    auto gasMat = desc.material(detElem.materialStr());
 
     // detector envelope
-    auto envShape = Tube(RIn, ROut, SizeZ / 2., 0., 2*M_PI);
-    Volume envVol("ce_MRICH_GVol", envShape, envMat);
+    Tube envShape(RIn, ROut, SizeZ / 2., 0., 2*M_PI);
+    Volume envVol("ce_MRICH_GVol", envShape, gasMat);
     envVol.setVisAttributes(desc.visAttributes(detElem.visStr()));
 
     // modules
+    addModules(envVol, detElem, desc, sens);
 
     // place envelope
     Volume motherVol = desc.pickMotherVolume(det);
@@ -56,6 +57,129 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
 }
 
 
+void addModules(Volume &mother, xml::DetElement &detElem, Detector &desc, SensitiveDetector &sens)
+{
+    xml::Component dims = detElem.dimensions();
+    xml::Component mods = detElem.child(_Unicode(modules));
+
+    auto ROut = dims.attr<double>(_Unicode(r_out));
+    auto mThick = mods.attr<double>(_Unicode(thickness));
+    auto mWidth = mods.attr<double>(_Unicode(width));
+    auto mGap = mods.attr<double>(_Unicode(gap));
+    auto InnerR = dims.attr<double>(_Unicode(inner_r));
+
+    auto modMat = desc.material(mods.materialStr());
+    auto gasMat = desc.material(detElem.materialStr());
+
+    // single module
+    Box mShape(mWidth/2., mWidth/2., mThick/2. - 0.1*mm);
+    Volume mVol("ce_MRICH_mod_Solid", mShape, modMat);
+
+    // a thin gas layer to detect optical photons
+    Box modShape(mWidth/2., mWidth/2., mThick/2.);
+    Volume modVol("ce_MRICH_mod_Solid_v", modShape, gasMat);
+    // thin gas layer is on top (+z) of the material
+    modVol.placeVolume(mVol, Position(0., 0., -0.1*mm));
+
+    modVol.setVisAttributes(desc.visAttributes(mods.visStr()));
+    sens.setType("photoncounter");
+    modVol.setSensitiveDetector(sens);
+
+    double MRICH_R, x_mrich = 0., y_mrich = 0;
+    int kmrich = -1;
+
+    // place modules in the sectors (disk)
+    auto points = fillSquares(Point(0., 0.), mWidth + mGap, InnerR, ROut + mGap);
+
+    // determine module direction, always facing z = 0
+    double roty = dims.z() > 0. ? M_PI/2. : -M_PI/2.;
+    int imod = 1;
+    for (auto &p : points) {
+        // operations are inversely ordered
+        Transform3D tr = Translation3D(p.x(), p.y(), 0.)        // move to position
+                       * RotationY(roty);                       // facing z = 0.
+        auto modPV = mother.placeVolume(modVol, tr);
+        modPV.addPhysVolID("sector", 1).addPhysVolID("module", imod ++);
+    }
+}
+
+// check if a square in a ring
+inline bool in_ring(const Point &pt, double side, double rmin, double rmax, double phmin, double phmax)
+{
+    if (pt.r() > rmax || pt.r() < rmin) {
+        return false;
+    }
+
+    // check four corners
+    std::vector<Point> pts {
+        Point(pt.x() - side/2., pt.y() - side/2.),
+        Point(pt.x() - side/2., pt.y() + side/2.),
+        Point(pt.x() + side/2., pt.y() - side/2.),
+        Point(pt.x() + side/2., pt.y() + side/2.),
+    };
+    for (auto &p : pts) {
+        if (p.r() > rmax || p.r() < rmin || p.phi() > phmax || p.phi() < phmin) {
+            return false;
+        }
+    }
+    return true;
+}
+
+// check if a square is overlapped with the others
+inline bool overlap(const Point &pt, double side, const std::vector<Point> &pts)
+{
+    for (auto &p : pts) {
+        auto pn = (p - pt)/side;
+        if ((std::abs(pn.x()) < 1. - 1e-6) && (std::abs(pn.y()) < 1. - 1e-6)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+// a helper function to recursively fill square in a ring
+void add_square(Point p, std::vector<Point> &res, double lside, double rmin, double rmax,
+                double phmin, double phmax)
+{
+    // outside of the ring or overlapping
+    if (!in_ring(p, lside, rmin, rmax, phmin, phmax) || overlap(p, lside, res)) {
+        return;
+    }
+
+    res.emplace_back(p);
+
+    // check adjacent squares
+    add_square(Point(p.x() + lside, p.y()), res, lside, rmin, rmax, phmin, phmax);
+    add_square(Point(p.x() - lside, p.y()), res, lside, rmin, rmax, phmin, phmax);
+    add_square(Point(p.x(), p.y() + lside), res, lside, rmin, rmax, phmin, phmax);
+    add_square(Point(p.x(), p.y() - lside), res, lside, rmin, rmax, phmin, phmax);
+}
+
+// fill squares
+std::vector<Point> fillSquares(Point ref, double lside, double rmin, double rmax, double phmin, double phmax)
+{
+    // start with a seed square and find one in the ring
+    // move to center
+    ref = ref - Point(int(ref.x()/lside)*lside, int(ref.y()/lside)*lside);
+
+    auto find_seed = [] (const Point &ref, int n, double side, double rmin, double rmax, double phmin, double phmax) {
+        for (int ix = -n; ix < n; ++ix) {
+            for (int iy = -n; iy < n; ++iy) {
+                Point pt(ref.x() + ix*side, ref.y() + iy*side);
+                if (in_ring(pt, side, rmin, rmax, phmin, phmax)) {
+                    return pt;
+                }
+            }
+        }
+        return ref;
+    };
+
+    std::vector<Point> res;
+    ref = find_seed(ref, int(rmax/lside) + 2, lside, rmin, rmax, phmin, phmax);
+    add_square(ref, res, lside, rmin, rmax, phmin, phmax);
+    return res;
+}
+
 // clang-format off
 DECLARE_DETELEMENT(ce_MRICH, createDetector)