Tech tree mods are very easy to do. Go ahead an do it.
Just take a look at the format of the existing files. It's not too hard to see how they did it and follow along. This mod was basically just a new multitek.txt file from what I remember.
The easiest way to work on a tech tree mod, is to extract multitek.txt from the VOL file, and place it in the OP2 directory. Edit the file as much as you want, and use the colony games to test it out. Then when it's ready to distribute, you'll probably want to rename it, and make a level that references it.
If you don't change the name, be prepared to expect checksum errors in multiplayer when someone with the mod tries to play someone without it. This can be rather annoying for people with only one install of OP2 that want to try your level and tech tree without mucking up their ability to play multiplayer. Even if you don't make a level, I suggest renaming it before distributing it, then they can always copy and rename it to multitek.txt to try it out. It'd be easy to delete that one file when they are done to go back to the original settings, and still keep your mod around under the different file name.
Some points to remember for tech tree mods.
- Follow the format in the files, and don't forget tags that you should have (like the end tag for each tech)
- Make sure the tech ID is a unique number
- Take a look at how techs are given for free at startup for each colony, and what techs they are not able to research. This is done by setting the research cost to 0 or -1. Which leads me to:
- A colony may be given techs for free that only the other colony can research. This basically lets you simplify your tech tree when both colonies can research a tech, but they have different prerequisits for it. By giving the prerequisite tech to the colony that can't research it, you avoid having to create two copies of that whole line of techs in your tech tree.
- The lab tag controls which lab the tech is researched at (basic, standard, advanced)
- If you want to force basic lab research before the standard lab is available, then make the standard lab tech rely on all techs that must first be researched at the advanced lab. You might want to take a look at the campaign tech trees instead of multitek.txt for an example of this.
- Rember that a tech will only appear for research once ALL of it's prerequist techs that you list for it have been researched.
- Most buildings in the game are buildable once you have the tech of the same name. Most of these techs are given for free (cost 0) at the start of the game. You may change this however to affect how and in what order buildings become available. If you know how to get the standard lab to appear after all basic lab research has been completed, then you probably have a very good idea how to work with this.
- The research cost can different between the eden and plymouth colonies. Instead of using a COST tag, you can use the cost tag that is specific to that colony. Make sure you specify a cost for both colonies however. Either through a single COST tag, or both individual tags. Note that this is used to make a tech available to only one colony.
- Certain tech IDs are hardcoded into the game engine. So don't change the tech IDs of existing techs with special affects that are not specified through the use of tags. Examples of this are the disaster warn techs. Colony morale techs also depend on hard coded tech IDs to determine when the morale effects kick in. (At least as far as I remember). The techs that give buildings also probably work this way.
- Techs given from wreckage must have a tech ID above a certain value. I think it was 8000 up to 8000 + 4095. You might want to do a search for info on this if you're unsure and plan to give a tech through collecting wreckage. (Also keep in mind when placing wreckage on a map, that it will only behave as wreckage on certain terrain types, so make sure you place it somewhere where it is recognized properly. If you're unsure and plan to do this, try doing a search for info on it).
