$upaxis
$upaxis is a QC command available in all 
Source games. It tells StudioMDL which axis should be considered 'up' in the model files below it. This is sometimes necessary because not every modeling package treats Z as the up axis, such as Maya. If unspecified, the up axis s Z.
Note:The command affects only animations & models below it.
Tip:You can use this to incorporate animations from different sources, if necessary, by changing which axis is considered 'up' on the fly.Syntax
$upaxis <X|-X|Y|-Y|Z|-Z>
Exporters
This command is mostly used by Valve for reorienting models created in Maya, which treats the Y axis as up unlike the game engine itself (and many other modeling packages), which use Z.
- These exporters generally need $upaxis (Don't usually treat the Z axis as 'up')
- Maya (Y)
- These exporters generally don't need $upaxis (Already treat the Z axis as 'up')
- XSI
- 3DS Max
- MilkShape 3D
- Blender
