Okay, so, I thought I understood this.  At least my numbers produced something that looked like it works on the another company F-16.

But then I installed the CS HUD on the Virtavia F-111 according to the numbers posted here -- and found out how it's really supposed to work.

On my F-16, when I move the eyepoint, the CS HUD moves with it.  If I move to the right or left, the HUD quickly slides off the glass in front of me.

This doesn't seem right.  And for sure:  On the F-111, when I slide to the left or right, the HUD image stays right where it is, and when I look at it from an angle, I see it's stuck to the glass and I'm seeing it from an angle.  With the F-16, looking from an angle, I see nothing!

The F-111 is acting like it should.  My F-16 numbers don't.   They look good from the front, but they aren't behaving like a 3D HUD in 3D space.  (Yes, I verified that it's CSWeapon!hud3d that I'm using.)

What the hell is going on?

Why does the F-111 work and the F-16 doesn't?  Carefully comparing the configuration I can see that on the F-111 the 1st and 3rd parameters of the collimation numbers are copied straight from the aircraft.cfg eyepoint -- like the manual says to do it.  The 2nd parameter - longitudinal axis - is 7 whereas the eyepoint says 23.7! (This should place the hud3d behind the pilot, no?  Or are those numbers backwards?))  And the hudfov3d for the F-111 is a MINUS 16.  This is apparently to flip it over.  A minus number on the F16 turns it upside down.

When I move my position in 3d space around, in the F-111 I can move forward right into the hud, and as I get closer, it gets bigger until I pass right through it.

On the F-16 I don't get closer to it until I get way in front of the jet, out where the nose is.  Then, the HUD is still in front of me, but I start to get closer and eventually pass thru it.  Once I get close to it, I can view it from an angle without it disappearing.

This is a clue to the puzzle.  I have to manipulate that 2nd parameter until I get it right.

But so far, no matter where I move it, I can't get it located where the VC HUD glass is located.  It always seems to be in front of the jet outside the cockpit.  When I make my number negative it flips over (which I can correct by making the hudfov3d negative too.)

Whew.  What a pain having to switch airplanes every time I make a change to it.

Dutch

Annnnd an update.  Just for fun, I restored the original non-CS another company F-16 HUD to see what it would do.  It does the same wrong thing, sliding off the glass when I shift right or left.  Even though some posts here talk about how it is "fully collimated".  And it shows the same location -- it's way in front of the jet too!  I have to move out to the nose cone to get close to it.  Wait...is that where the model is placing the rectangle?  Way out there?  Why?

Yet, the CS HUD in the F-111 works perfectly!  Except it's a dark and not light green.  Why?

Baffled.