伪球

static void drawPoints(const AcGePoint3dArray &pts, short color)
  {
    AcDbDatabase *pDatabase = acdbHostApplicationServices()->workingDatabase();
    AcDbBlockTableRecordPointer pBlockTableRecord(pDatabase->currentSpaceId(),AcDb::kForWrite);
    for(size_t i=0 ; isetColorIndex(color);
      if(pBlockTableRecord->appendAcDbEntity(pPoint) != eOk)
        delete pPoint;
      else
        pPoint->close();
    }
  }
  //Pseudosphere
  //By Roger Bagula
  //C source by Paul Bourke
  //http://local.wasp.uwa.edu.au/~pbourke/geometry/pseudosphere/
  static void BrxVsArx_doit(void)
  {
    int i,j;
    int n = 250;
    double theta1,theta2;
    double phi1,phi2;
    double x,y,z;
    AcGePoint3dArray pts;
    for (i=0;i<n;i++) {
      theta1 = -PI + TWOPI * i / (double)n;
      theta2 = -PI + TWOPI * (i+1) / (double)n;
      for (j=0;j<2*n;j++) {
        phi1 = -TWOPI + 2 * TWOPI * j / (2.0*n); 
        phi2 = -TWOPI + 2 * TWOPI * (j+1) / (2.0*n);
        x = phi1-tanh(phi1);
        y = sech(phi1)*sin(theta1);
        z = sech(phi1)*cos(theta1);
        pts.append(AcGePoint3d(x,y,z));
        x = phi1-tanh(phi1);
        y = sech(phi1)*sin(theta2);
        z = sech(phi1)*cos(theta2);
        pts.append(AcGePoint3d(x,y,z));
        x = phi2-tanh(phi2);
        y = sech(phi2)*sin(theta2);
        z = sech(phi2)*cos(theta2);
        pts.append(AcGePoint3d(x,y,z));
        x = phi2-tanh(phi2);
        y = sech(phi2)*sin(theta1);
        z = sech(phi2)*cos(theta1);
        pts.append(AcGePoint3d(x,y,z));
      }
    }
    drawPoints(pts,1);
    pts.removeAll();
    for (i=0;i<n;i++) {
      theta1 = -PI + TWOPI * i / (double)n;
      theta2 = -PI + TWOPI * (i+1) / (double)n;
      for (j=0;j<2*n;j++) {
        phi1 = -TWOPI + 2 * TWOPI * j / (2.0*n);
        phi2 = -TWOPI + 2 * TWOPI * (j+1) / (2.0*n);
        x = (phi1 - tanh(phi1)) / (phi1*phi1 - 2 * tanh(phi1) + 1); 
        y = -sech(phi1) * sin(theta1) / (phi1*phi1 - 2 * tanh(phi1) + 1);
        z = -sech(phi1) * cos(theta1) / (phi1*phi1 - 2 * tanh(phi1) + 1);
        pts.append(AcGePoint3d(x,y,z));
        x = (phi1 - tanh(phi1)) / (phi1*phi1 - 2 * tanh(phi1) + 1);
        y = -sech(phi1) * sin(theta2) / (phi1*phi1 - 2 * tanh(phi1) + 1);
        z = -sech(phi1) * cos(theta2) / (phi1*phi1 - 2 * tanh(phi1) + 1);
        pts.append(AcGePoint3d(x,y,z));
        x = (phi2 - tanh(phi2)) / (phi2*phi2 - 2 * tanh(phi2) + 1);
        y = -sech(phi2) * sin(theta2) / (phi2*phi2 - 2 * tanh(phi2) + 1);
        z = -sech(phi2) * cos(theta2) / (phi2*phi2 - 2 * tanh(phi2) + 1);
        pts.append(AcGePoint3d(x,y,z));
        x = (phi2 - tanh(phi2)) / (phi2*phi2 - 2 * tanh(phi2) + 1);
        y = -sech(phi2) * sin(theta1) / (phi2*phi2 - 2 * tanh(phi2) + 1);
        z = -sech(phi2) * cos(theta1) / (phi2*phi2 - 2 * tanh(phi2) + 1);
        pts.append(AcGePoint3d(x,y,z));
      }
    }
    drawPoints(pts,5);
  }
  inline double static sech(double d)
  {
    return(1.0 / cosh(d));
  }

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