Need some help with the compass


#1

I need to understand HiFi’s conventions for agent yaw and its perceived direction.

Agent yaw = 0.0 Is that North?
Agent yaw = 90.0 Is that East?
Agent yaw = 180.0 Is that South?
Agent yaw = -90.0 Is that West?

I understand it runs -180 … 0 … 180 vs 0 …360

Place a compass - North tickmark aligned with 0.0 yaw. Rotate 90 degrees clockwise for East. Yaw = -90.0, another 90 for South = 180, another 90 for West = -90, another 90 for North = 0. I would have thought 0, 90, 180, -90, 0. It seems bacwards and explains why my sun script and shadows don’t seem to match RL expectations. Maybe there’s a reason for this like Z not being up… but it’s odd.


#2

As far as I know, there isn’t an official “north”. There’s just x, z, and y directions. (I agree, the x-z-y coordinate system is not very user friendly.)

But if you equate “north” to mean 0 deg yaw then:
-90 deg = east
+90 deg = west
180 deg = south

Counterintuitively(?), 0 deg yaw is pointing in the negative z-axis direction.

You can see how yaw relates to the axes if you position your avatar near /0,0,0.


#3

Yeah - it has a perverse logic - but I’m not really sure the shadows, new sun and current system all actually are on the same page. Now that we have moving sun that actually computes a reasonably realistic RL setup… it would be nice to have a semi-official definition of N-S-E-W and insure all the bits that care about such things (Shadows, sun) agree upon it.