you will need:
sparkedit (to move the vehicles around to your likeing)
HMT 3.5
HHT (for c-dropship)
A willing to learn brain
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1)On your desktop create a folder named PMI.
2)Inside it make 4 folders named: Batch Extract, Build, New Items, VIB.
3)open HMT and your multiplayer map that you are going to use. MAKE SURE THIS MAP IS COMPLETELY UNMODDED. In this case it's Deathisland.
4)click tools>extract>batch extract. Check the box that says "Extract Metadata". save this to the batch extract folder. click YES when it asks you to extract the BSP
5)Than click tools>extract>BSP/model sections. Save this to the VIB folder.
6)now is when it gets a bit harder, open the SP map (in this case its B40).
7)go down to the [vehi] tag and click on c_dropship/c_dropship check the recursive box at the top and click save meta (to the left of the recursive box). save this to the new items folder.
8)repeat step 7 but with pelican/pelican instead of c_dropship.
9)repeat step 8 but with wraith/wraith instead of pelican.
10)Go to Generate raw model offset list (CSV file). save this to your PMI folder (anywhere is OK just as long as you save it somewhere).
11)Go to tools>extract>raw model and load the CSV file you just saved. Now locate vehicles/c_dropship/c_dropship and extract this to PMI>New items>vehicles>c_dropship.
12)now still in the CSV file find vehicles/pelican/pelican. save this to PMI>New items>vehicles>pelican.
13)now finally STILL in the CSV file find the vehicles/wraith/wraith. save this to PMI>New items>vehicles>wraith.
14)now you can close out of the CSV file and click tools>model decraper/BSP builder. Right click on the big box and click ADD. go to PMI>New items>vehicles>c_dropship and add the mod2.meta.
15)right click on the big box again and click add. find the mod2.meta in PMI>New items>vehicles>pelican and add it.
16)now add the mod2.meta from PMI>New items>vehicles>wraith.
17)click the browse by the existing vertex area box and go to PMI>VIB and double click on dethisland.verticies. do the same thing with index and BSP block.
18)click De-crap these models and build a new BSP chunk while you're at it.
19)minimise HMT and go to your PMI>VIB folder. there should be 6 items in there. if not, than you messed up on the de-crapper. If there IS 6 items than find the deathisland.sbsp.meta Copy it and go to the PMI>Batch extract>levels>test>deathisland folder and paste it there.
20)OK now time to get the build folder in action. first copy every folder in the batch extract folder to the build folder. when that is done go to the new items folder and copy everything from there and paste it into the build folder. click Yes to all when it asks you if you want to overight the folders. Add the completely unmoded deathisland in the build folder as well.
21)OK now for the hardest part in the tutorial. click tools>rebuild map. for the map file add the deathisland from the build folder. click yes for auto fill.
22)this is the hard part. on the bottem of the screen click ADD. go to PMI>build>vehicles>c_dropship.
22.5)add everything there. NOT THE 4 FOLDERS. after you did that click add again and click the bitmaps folder and add everything from in there. do that with cd_gun, effects, and shaders too.
23) click Add again and go to PMI>build>vehicles>pelican and repeat the steps of 22.5. there is no cd_gun in this one of course.
24)once again click Add and go to PMI>build>vehicles>wraith and repeat the steps of 22.5. there is no cd_gun in this one of course.
25.1)click rebuild.
25.3)when it asks you about new verticies click YES and go into PMI>VIB and click on deathisland.verticies.new.
25.7)when it asks you about new indicies click YES and go into PMI>VIB and click on deathisland.indicies.new.
26)click OK when it asks you about the offset
27)if all goes well than at the end it will say map rebuilt successfully.
28)go to the PMI>build folder and copy deathisland.map.rebuild.map and put it in you halo maps directory. delete the deathisland.map and rename the rebuilt map deathisland.map
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MAKEING THE VEHICLES DRIVIBLE
right now NONE of the vehicles are even rideable by MasterChief. Were going to fix that.
open deathisland.map and go to the [vehi] tag. click on the c_dropship. scroll down on the tag editor and select seat 0. change the name to W-driver. now with seat 1-8 (the cargo seats) change them all to W-gunner. it uses the gunner model so it kind of looks like you are holding on to somthing while flying.
now for the pelican. make seat 0 W-driver. and seat 1-8 B-driver. (makes it look like you are lieing down on the seats).
and now the wraith. make seat 0 W-driver again. and you are all set.
IMPORTANT NOTE: if the vehicles cannnot move at all when you are driving them than you must change it to the right vehicle ID. for c_dropship and pelican change them to dropship/pelican in the tag editor. for the wraith make it ghost/wraith.
ANOTHER IMPORTANT NOTE: to be able to get into the c_dropship you must go to HHT. find the [vehi] tag in c_dropship. scroll down. you should see about 10 actv tags. one isn't nulled out. make the one that isnt nulled and you can drive it. The reason for this is because the gun on the c_dropship is counted as an enemy, therefore you cannot enter the vehicle.
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getting it INTO the map PT. 1. For this part you must sacrifice vehicles you dont really need. like the banshee since you can fly in both dropships, and the turret since NOBODY uses it.

go to HMT and find the [vehi]c_dropship tag. copy its meta and paste it over the banshee's. MAKE SURE YOU ARE POSTING IT OVER THE BANSHEE_MP NOT THE NORMAL BANSHEE.
now go to the [vehi]pelican tag. copy its meta and paste it over the c gun turret.
now find the wraith tag and paste its meta over..umm.. lets go with the chaingun warthog. you can use it with the ghost or the other warthog if you like.
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getting the vehicles into the map PT.2.for this part you will need sparkedit.
open up sparkedit and open deathisland.map. make as many vehicles as you want but take heed: it WILL be laggy at the start. and if there is too much than it will be laggy for the whole game. keep the turret, the banshee and the chaingun warthog without changing it to the added vehicles, as if you do change it they will not appear.
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OK you may have noticed a new BIPD. the cd_gun. This is indeed an AI. if you want you can make seats on vehicles have them in it. they will only move in banshees and dropships. to add them go to HHT and find the vehi you want to add them in. make the actv tags (not the first one near the top) the cd_gun. when you start the game the vehicles will have them in it. in one map the max of them is about 25 altogether