View source for Working ladders

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== Introduction ==
In all [[Source]] games (except [[Team Fortress 2]] and [[Portal 2]], which have no ladders) a ladder in-game consists of the prop or brush that the player perceives as the ladder, and the invisible entity/brush system in front of it that actually makes the ladder climbable. This gives the illusion that the player is climbing the visible ladder, where in fact he is scaling the invisible ladder entity/brush just in front of it.

=== Creating the visible ladder ===

To create the visible ladder, you can either use
* a [[prop_static]] entity with a ladder model (like ''models\props_c17\metalladder001.mdl''), or
* a brush with a ladder texture (like ''metal/metalladder001a'').

=== Climbing system ===
How the ladder's climbing system is created depends on which Source game it is intended for. Ladders in [[Half-Life 2]] and [[Half-Life 2: Deathmatch]] are created a little differently than those of earlier games to provide better control for the level designer and player alike, while ladders in [[Counter-Strike: Source]] and [[Day of Defeat: Source]] are implemented pretty much the same way as the older games.
For how to create ladders for Counter-Strike: Source and Day of Defeat: Source, see [[#Ladders_for_Counter_Strike:_Source_and_Day_of_Defeat:_Source|below]].

== Ladder entities for Half-Life 2 series / Half-Life 2 Deathmatch ==

To create a ladder you must define the volume in which the player will move through space while on the ladder. This volume can be defined in two ways: Using the [[func_useableladder]] entity, or using the deprecated [[func_ladderendpoint]] entity (which is only briefly described below to provide understanding of the workings of older maps).

The func_useableladder entity can be divided into two sub entities: a starting point and an ending point ''(See Fig. 1a)''. Their positions can be typed into the keyvalue fields, or more typically the ladder volume can be defined using the visual ladder tool, by dragging its center circle that is visible when the entity is selected ''(See Fig. 1b)''. Using this tool you can drag the start and end point of the ladder into appropriate positions in the 2D view. The ladder's start and ending point may be of arbitrary orientation and length ''(See Fig. 1c)''. Simply pull the endpoints where you want them and the player will move between these points while on the ladder.

{| border=0 cellspacing=0 cellpadding=0
| [[Image:hammer_ladders1.jpg|frame|left|Fig. 1a - Ladder points (using two <code>func_ladderendpoint</code>s)]]
| [[Image:hammer_ladders2.jpg|frame|left|Fig. 1b - Changing orientation]]
| [[Image:hammer_ladders3.jpg|frame|left|Fig. 1c - Slanted ladder points]]
|}

As you place the endpoints, make sure that you place them a couple of units away from the visible ladder brush (or any other brush or model) because if any four sides of the ladder volume is even touching against a surface of a brush or a model, this will make that part of the ladder volume unclimbable.

The now obsolete func_ladderendpoint entity just consists of a single endpoint. A ladder volume is created by linking two func_ladderendpoints together using their properties. A ladder volume is created between two func_ladderendpoints by naming one of the endpoints and having the other endpoint point to its name in its ''Other'' value. (It is not necessary for the second endpoint to point back at the first as stated in properties.)

=== Dismounts ===

[[Image:hammer_ladders4.jpg|frame|left|Fig. 2 - Dismounts]]

Along with the volume of movement, you can also provide dismount points for the ladder ''(See Fig. 2)'' to allow easier and more controlled dismounts. These points are marked using the [[info_ladder_dismount]] entity. While next to and facing one of these markers, the player can press his use key to dismount to the position of the marker (typically when ladders run between more than two floors). If he has reached one of the ends of the ladder, he can also simply walk off the ladder by facing one of the markers nearby and walking forward.
You can use multiple info_ladder_dismount markers for each dismount place to provide more directions to exit the ladder in.

To avoid possible confusion between nearby ladders using different dismount markers, each info_ladder_dismount entity has a property value called ''LadderName'' which can be used to contain the name of the ladder it belongs to.

Like the ladder volume, the dismount points must be free of obstruction and allow the player to stand at their position without intersecting solid world geometry.<br style="clear:left;"/>

=== In-game testing ===

Once you have created your ladders, you can compile your map and test them. If you wish, you can also display the ladder entities in-game along with some debug information by opening the console and typing <code>sv_showladders 1</code> to enable this, and then load or reload (by typing <code>restart</code>) the map you wish to view.
This will show you all the start and end points of the ladders (func_useableladder and func_ladderendpoint entities), as well as the dismount points (info_ladder_dismount entities) ''(See Fig. 3a)'', and can help you determine if these entities are set up properly, if ladder entities are colliding with solid world geometry or the prop model of the ladder itself ''(See Fig. 3b)'', and which func_ladderendpoint entities connect to each other.

{| border=0 cellspacing=0 cellpadding=0
| [[Image:hammer_ladders5.jpg|frame|left|Fig. 3a - In-game visualization (<code>sv_showladders 1</code>)]]
| [[Image:hammer_ladders6.jpg|frame|left|Fig. 3b - Endpoint stuck in floor]]
|}

=== How ladders work in-game ===

The safest way to mount a ladder in Half-life 2 is to approach its invisible ladder volume and within reaching distance press the use key. This will automatically position you on the ladder. (You can also walk into the ladder volume, with greater risk of missing it and falling down any hole.)

To dismount a ladder you can always either jump off, or press your use key. If the ladder has info_ladder_dismounts, you can also simply walk off from its endpoints, and pressing your use key while next to and facing an info_ladder_dismount will also allow more controlled dismounts anywhere on the ladder.

== Ladders for Counter Strike: Source, Day of Defeat: Source and Garry's Mod ==

Create another brush in front of the object/brush you want to be climbable, as close as you can to it, but without touching it. Make sure that the face is the same width/height as the climbable object. Assign the material '''tools/toolsinvisibleladder''' to this brush and then tie it to an entity (CTRL+T). Select [[func_ladder]] from the Object Properties dialog. You now have a climbable face which is in front of the object/brush.

{{bug|If the brush crosses any water surfaces, the player interacting with it can exhibit weird behavior, teleport the player while in the water to the end of the ladder. This has been encountered in a partial submersion of the ladder brush. In Counter-Strike: Source}} {{todo|In what circumstances exactly does it happen?}}

{| border=0 cellspacing=0 cellpadding=0
| [[Image:Cssladderprop01a.png|frame|left|Fig. 4 - [[func_ladder]] textured with '''tools/toolsinvisibleladder''' in front of a [[prop_static]] ladder.]]
|}

While on a ladder in CS:S your shooting accuracy will be significantly reduced.

The similar ladders using in Half-Life 1, but there is '''AAATRIGGER''' texture used instead of '''tools/toolsinvisibleladder'''.

== Ladders for Counter Strike: Global Offensive ==
See:
* [[Creating_Ladders_(CSGO)]]

== Ladders for Left 4 Dead & Left 4 Dead 2 ==
Read the folowing tutorials, to create Ladders in Left 4 Dead & Left 4 Dead 2:
*[[L4D_Level_Design/Ladders|Creating Ladders for the Left 4 Dead series]]
*[[L4D_Level_Design/Versus_Maps#Making_Infected_Ladders_Visible|Creating Infected only Ladders]]

== Optimizing Ladders ==
The ladder props, like every prop_static, default to using [[VPhysics]] for collision detection, which will provide more detailed physics collisions, but in some cases this might not be preferable. In multiplayer maps and very resource demanding maps using VPhysics props costs precious resources, and you might want to sacrifice good physics to avoid potential lag. Here are some good methods to minimize resource cost:

*If the ladder is for HL2 or HL2:DM, and the ladder is straight, the best method depends on whether somebody is going to be able to shoot through the ladder. If they are not (like if the ladder is against a wall) you could simply change the ''Collisions'' keyvalue to ''Use Bounding Box''. If they are, you could change the keyvalue to ''Not Solid'' and place an invisible Clip (''toolsclip'') to detect collision with it instead.

*If you are creating a slanting ladder for HL2 or HL2:DM, a bounding box will not rotate with the prop, and will obstruct the climbing system, in which case you are better off making the ladder prop ''Not Solid'' and place an invisible, rotated Clip (''toolsclip'') or Player Clip (''toolsplayerclip'') textured brush alongside the ladder (depending on whether or not somebody is going to be able to shoot through it).

*If the ladder is for a CS:S or DoD:S map, you could change the ''Collisions'' keyvalue to ''Not Solid'' and make the func_ladder brush cover the ladder prop, rotating it if necessary.

In multiplayer maps it's also an understood expectation to be able to move freely parallel to the surface that a ladder covers. When it comes to brush based ladders, you can get away with turning the ladder brush into a non-solid [[func_brush]] to avoid players getting temporarily "stuck" against the side of the ladder, but when it comes to prop ladders, they are often too protruding from the wall to make a player standing inside a ladder believable. In that case you are probably better off using two Player Clip textured wedges at the sides of the prop, guiding the player to the front of the prop.

If nothing else, you could turn a brush ladder into a [[func_detail]] to avoid unnecessary brush leafs.

== Examples ==
'''HL2/HL2:DM'''
*[[ladder_simple]] - A prefab containing a complete ladder setup.
*[http://nudel.omega2k3.de/maps/?s=download&act=view&fileID=21 LaddersHL2.zip]{{Template:Dead link}} (6k)
<!-- SDK nuts has closed. When (and if) these tutorials are ported onto the VDC, please link to them instead!
*[http://www.sdknuts.net/akg/tutorials/wiseladder.asp HL2 Ladders]
-->

'''CS:S/DoD:S'''
*[http://type3studios.com/downloads/tutorials/SdkNutsTutorials/LadderCSS.zip LaddersCSS.zip] (7k)

== See also ==
*[[func_useableladder]]
*[[func_ladderendpoint]]
*[[info_ladder_dismount]]
*[[func_ladder]]

[[Category:Level Design Tutorials]]