Hi,

I have gathered some performance data for the calculation of the intersecting volume between an elliptical cross-section cylinder (tgc) and a hexahedron (arb8) using gqa in MGED. I created a 100x scaled version of the same model and again used gqa to calculate the volume. I used the following command to get the volume and time (time "gqa ..."):

gqa -Av -g XX int.c

where XX is the grid spacing I used except for the default case.

I see that the default 0.25 lower limit for the grid size is not optimal for either the original or the 100x scaled version of the model. Also, I can get to within 0.3% error in 0.05s for the small model but for the 100x model requires more than 0.15s to get to the same error level. Here is the data in a table (hoping the formatting will stay as it is)

Characteristic Size | 1 | 100 | ||||

V Actual | 0.7853982 | 785398.2 | ||||

Grid Size (% of charc. Size) | Volume | Time (microsec) | % error | Volume | Time (microsec) | % error |

Def. Grid Size (0.25 abs lower limit) | 0.731724 | 23535 | -6.8% | 787744 | 368938 | 0.3% |

10.0% | 0.76912 | 38972 | -2.1% | 834063 | 25095 | 6.2% |

5.0% | 0.78306 | 51085 | -0.3% | 811749 | 41145 | 3.4% |

2.5% | 0.78539 | 85981 | 0.0% | 799036 | 67201 | 1.7% |

1.0% | 0.785166 | 187265 | 0.0% | 790717 | 162074 | 0.7% |

0.5% | 0.785536 | 404860 | 0.0% | 788228 | 298249 | 0.4% |

I also need to calculate the center of gravity for the combination but I can't seem to find out how to assign the density and then get the center of gravity/moments of inertia information.

Any help with the volume calculation accuracy and speed as well as the density assignment and center of gravity calculations is much appreciated.

Thanks,

Harun