Why do i need to make one then... i' m a bit confused

Because in the totoial they say:
Quote: "Open a diffuse texture in Photoshop to be used as a segment floor, wall or ceiling. In the bottom right corner panel select the ‘Channels’ tab and select icon ‘Create new channel’ to create an alpha channel for your texture as shown below. The alpha channel should be white (see section 6 for changing channel properties"
I was thinking that that was the probleme, because when i created a segment with firma it didn' t show up in X10...
IV