Alright here is a quick and dirty tutorial on how to add engine trails or engine glows on a ship.
Obviously, you first need CFHodEd. This tutorial is using CFHodEd v3.2.4, but should work on any recent version. You are expected to master the basics of CFHodEd (aka placing hardpoints, importing/exporting/transforming meshes) and HW2 modding in general.
Let's start on engine trails and burns. The ship used here is the derelict light corvette, featured as an interceptor in the Onslaught mod by Durandel, and hodded by LeviathansWrath.
EDIT : Added link to the finished product at the bottom of the post.
1st step : add the necessary engine nozzles hardpoints on your ship.
The naming convention is critical. You must name your hardpoints EngineNozzle#, with # from 1 to 9. HW2 doesn't seem to handle more than 9 nozzles.
Note the 180 degree rotation on the Y axis. It has its importance for the engine burns, so make sure you correctly set it.
2nd step : export an engine burn mesh from a vanilla ship (preferably with an engine of similar size). Here, the Vaygr Assault Craft.
3rd step : create a new engine burn slot on your ship and import here the mesh you just exported. Make sure you assign it to the correct hardpoint.
While this is not over yet, you can now save your hod. Let's move on the .ship file a bit.
4th step : set the burn flare in the .ship file.
Make sure you have something that looks like that in there. You can copy-paste this line from a vanilla ship and/or have a look here to see the different settings available.
setEngineBurn(NewShipType, 7, 0.5, 1, 15, 0, 0.7, 0.1, 20)
You need only one of this line, even if your ship has several engine burns.
And now, ingame.
If you did everything correctly, you should see this flare behind your ship. Congratulations, you accomplished the first part of this tutorial !
Now, the actual trail.
5th step : export an engine shape mesh from a vanilla ship. Preferably the same as before.
6th step : create a new engine shape slot on your ship and import here the mesh you just exported. Make sure you assign it to the correct hardpoint.
7th step : set the engine trail in the .ship file.
Specifics for those can be found here.
setEngineTrail(NewShipType, 0, 2, "trail_ribbon.tga", 0.1, 0.5, 0.025, 6)
Contrary to the burns, you need one of these for each engine trail your ship features. On the other hand, having more lines than the number of actual trails on your hod will result in debug warnings that will appear in your hw2.log or as popups in windowed mode, as every other debug warnings/errors. As warnings, they don't cause crashes, however try to avoid it, it's bad design.
The moment of truth : load your game.
If you see that, then you're done. Wasn't as hard as it sounds, was it ?
EDIT : Here is the finished hod so you can have your hands on the final result yourself. : http://www.mediafire.com/?zwmvwytzrnz
Engine glows are to come later. Hoping it'll be useful .