FWPFMaths.cc

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#include <cmath>
#include "TMath.h"
#include "TEveVector.h"

namespace FWPFMaths {
  //______________________________________________________________________________
  float sgn(float val) { return (val < 0) ? -1 : 1; }

  //______________________________________________________________________________
  TEveVector cross(const TEveVector &v1, const TEveVector &v2) {
    TEveVector vec;

    vec.fX = (v1.fY * v2.fZ) - (v1.fZ * v2.fY);
    vec.fY = (v1.fZ * v2.fX) - (v1.fX * v2.fZ);
    vec.fZ = (v1.fX * v2.fY) - (v1.fY * v2.fX);

    return vec;
  }

  //______________________________________________________________________________
  float dot(const TEveVector &v1, const TEveVector &v2) {
    float result = (v1.fX * v2.fX) + (v1.fY * v2.fY) + (v1.fZ * v1.fZ);

    return result;
  }

  //______________________________________________________________________________
  TEveVector lineCircleIntersect(const TEveVector &v1, const TEveVector &v2, float r) {
    // Definitions
    float x, y;
    float dx = v1.fX - v2.fX;
    float dy = v1.fY - v2.fY;
    float dr = sqrt((dx * dx) + (dy * dy));
    float D = ((v2.fX * v1.fY) - (v1.fX * v2.fY));

    float rtDescrim = sqrt(((r * r) * (dr * dr)) - (D * D));

    if (dy < 0)  // Going down
    {
      x = (D * dy) - ((sgn(dy) * dx) * rtDescrim);
      x /= (dr * dr);

      y = (-D * dx) - (fabs(dy) * rtDescrim);
      y /= (dr * dr);
    } else {
      x = (D * dy) + ((sgn(dy) * dx) * rtDescrim);
      x /= (dr * dr);

      y = (-D * dx) + (fabs(dy) * rtDescrim);
      y /= (dr * dr);
    }

    TEveVector result = TEveVector(x, y, 0.001);
    return result;
  }

  //______________________________________________________________________________
  TEveVector lineLineIntersect(const TEveVector &p1, const TEveVector &p2, const TEveVector &p3, const TEveVector &p4) {
    TEveVector a = p2 - p1;
    TEveVector b = p4 - p3;
    TEveVector c = p3 - p1;
    TEveVector result;
    float s, val;

    s = dot(cross(c, b), cross(a, b));
    val = dot(cross(a, b), cross(a, b));
    s /= val;

    result = p1 + (a * s);
    return result;
  }

  //______________________________________________________________________________
  float linearInterpolation(const TEveVector &p1, const TEveVector &p2, float z) {
    float y;

    y = ((z - fabs(p1.fZ)) * p2.fY) + ((fabs(p2.fZ) - z) * p1.fY);
    y /= (fabs(p2.fZ) - fabs(p1.fZ));

    return y;
  }

  //______________________________________________________________________________
  bool checkIntersect(const TEveVector &p, float r) {
    float h = sqrt((p.fX * p.fX) + (p.fY * p.fY));

    if (h >= r)
      return true;

    return false;
  }

  //______________________________________________________________________________
  float calculateEt(const TEveVector &centre, float e) {
    TEveVector vec = centre;
    float et;

    vec.Normalize();
    vec *= e;
    et = vec.Perp();

    return et;
  }
}  // namespace FWPFMaths