Hi(adsbygoogle = window.adsbygoogle || []).push({});

I'm having trouble to fully understand the concept of Genus: https://en.wikipedia.org/wiki/Genus_(mathematics)

Those examples are preety simple to me Genus = number of handles/holes. But what the wikipedia doesn't cover (at least visually) is when these handles or holes share space like in the last 3 examples of the image below:

TopMod is a modeling program that has a display that shows how many Genus the present mesh has.

I was expecting different numbers honestly...

I cant get a rational grasp to understand the rules of these numbers.

http://forums.newtek.com/images/smilies/brians/help.gif [Broken]

It seems that it's the number of possible exits there is when going through a hole of the mesh.

So the Single Y shape has Genus 2 because when I go through Hole-number-1 I can exit on Hole-number-2 or Hole-number-3, so 2 possibilities.

The Double Y shape has Genus 4 because it's the previous situation but independent and doubled.

Is this it?

Cheers

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# [Help] Genus: Having difficulty to fully understand it.

**Physics Forums | Science Articles, Homework Help, Discussion**