Figuring out the enemy projectile origin

For my Terminal Velocity remake I'm currently aiming to get more behaviours sorted out. Specifically, the behaviour behind these turrets (and some tanks in other levels):

The behaviour is simple enough, but it was quickly clear that one thing was wrong: the origin position of the projectile. When I worked on the first enemy type I just fired from the center of the enemy, which seemed to be fine enough. But these guns have the origin at the base of the mesh and the projectiles should obviously be coming from the turret end.

This lead to the question of "where is this position stored?" The game has what I call "entity definition" blocks, but nothing in that was a usable position. So there must be something else that indicates this position.

I needed more info, so my next step was to expand my memory monitor. I have made a tool that can read DosBox memory and I have identified specific locations already to track useful information. I expanded this to help me search for approximate memory values (luckily these guns shoot projectiles that travel with an unchanging height/Y coordinate), and this allowed me to track down where projectiles are kept in game memory. Now I knew the exact world Y coordinate of these projectiles, and from that I could determine the relative Y coordinate.

Now I had a value to look for, but I still needed to find where its source is. At some point I had a look at the mesh of the gun, and one thing stood out: there is actually a vertex pretty much where the projectile would start. Could the origin position be a vertex reference?

With this idea I dove back into the mesh file, and looked for vertices with a Y coordinate close to what I had found earlier, and I identified a handful of these. Then I went back to the entity definition and there was exactly one integer that matched one of those vertices. Going with the guess, I made an addition to put a small sphere at the origin location just to see if it's right.

And as you can see here, spot on!

Now there's another thing. For the unknown value in the entity where I found the vertex reference I already figured out that it is a variable length array, and while looking at the level I noticed that another entity in this level ended up with multiple spheres.

Could it indeed be that that unknown value simply indicates all projectile origins via vertex references? I loaded up the game, found this enemy in the actual level, and saw that indeed it was shooting from the wingtips, alternating! With this I could remove another value from the "unknown" list.