Tutorial on adding custom objects to MTA:SA

First of all you'll need to put your custom objects (DFF, TXD and COL) into MTA San Andreas 1.1\server\mods\deathmatch\resources\[editor]\editor_main\.

Then open MTA San Andreas 1.1\server\mods\deathmatch\resources\[editor]\editor_main\meta.xml and add these like the other objects:
[code]
	<file src="yourobject.dff" />
	<file src="yourobject.col" />
	<file src="yourobject.txd" />
[/code]

After that, open samp_models_lsoffice.lua in the same folder (or create a new file if you want).
Add this like the other objects:
[code]
	txd1000 = engineLoadTXD('yourobject.txd')
	engineImportTXD(txd1000, the_replaced_object_model_id)
	col1000 = engineLoadCOL('yourobject.col')
	dff1000 = engineLoadDFF('yourobject.dff', 0)
	engineReplaceCOL(txd1000, the_replaced_object_model_id)
	engineReplaceModel(txd1000, the_replaced_object_model_id)
	engineReplaceCOL(txd1000, the_replaced_object_model_id)
[/code]
If you create a new script instead of editing samp_models_lsoffice.lua, you'll need to do this:
[code]
rootElement = getRootElement()
function loadobj(resource)
	if resource ~= getThisResource() then return end
	txd1000 = engineLoadTXD('yourobject.txd')
	engineImportTXD(txd1000, the_replaced_object_id)
	col1000 = engineLoadCOL('yourobject.col')
	dff1000 = engineLoadDFF('yourobject.dff', 0)
	engineReplaceCOL(txd1000, the_replaced_object_id)
	engineReplaceModel(txd1000, the_replaced_object_id)
	engineReplaceCOL(txd1000, the_replaced_object_id)
end
addEventHandler('onClientResourceStart', rootElement, loadobj)
[/code]
and then go back to MTA San Andreas 1.1\server\mods\deathmatch\resources\[editor]\editor_main\meta.xml and add/uncomment the script so that it can be loaded in map editor:
[code]
	<!--SA-MP Objects -->
	<script src="samp_models_lsoffice.lua" type="client"/>
	<script src="your_own_script_name_if_you_create_a_new_one.lua" type="client"/>
	<!--<script src="samp_models_rc3_1.lua" type="client"/>-->
	<!--<script src="samp_models_rc3_2.lua" type="client"/>-->
    	<!--<script src="samp_models_rc4.lua" type="client"/>-->
	<!--<script src="samp_models_rc5.lua" type="client"/>-->
[/code]
Then open MTA San Andreas 1.1\server\mods\deathmatch\resources\[editor]\editor_gui\client\browser\objects.xml
and add a new category, or append to the old categories if you want to:
[code]
		<group name="Custom objects">
			<object model="the_replaced_object_model_id" name="Your first custom object in MTA:SA" keywords=""/>
		</group>
		<group name="Enterable LS Building">
			<object model="4587" name="LSOffice1" keywords=""/>
			<object model="3781" name="LSOffice1Floors" keywords=""/>
			<object model="4605" name="LSOffice1Glass" keywords=""/>
		</group>
[/code]
Done. Note that I use MTA:SA 1.1 as example. If you use 1.0.5, the path will be a little bit different, but I think it is not hard to find the folder of the map editor.