Introduction
Ever notice your terrain map or map with a large open area bogs down incredibly when you play with bots - even though your r_speeds are low and your fps high? This tutorial is for Quake 3 mappers who want bots to run faster - that is - use LESS CPU on their maps.  This tutorial is meant to be a more visual companion to a somewhat more detailed text-only tutorial on bot optimization at the Team Huh Quake 3 site.  While this tutorial should be useful to all Quake 3 mappers (mods included) wanting further details on bot optimization, it focuses on the issue of optimizing maps with at least one large open area (including terrain) in particular.  The mapfile for this tutorial can be found here

Concepts

• clip brushes - these are brushes which have one of many different types of /common/*.clip applied to all sides of  a brush which also makes the brush invisible.  Clips known to assist in reducing bot cpu usage are botclip (treated as solid by bots), playerclip (treated as solid by players but player can still shoot through it), and fullclip (treated as solid by everything) - others may work but have not been tested here
• bspc (not to be confused with bsp)- this is the program which creates your aas file (comes with most map editors - e.g. gtkBuild) - it is where all the areas and clusters are defined
• .aas - this is the output file created by bspc which allows bots to navigate maps: e.g. mymap.aas
• area - bspc divides the map into areas which are used by bots to make "decisions" about where to go - also called "reachability areas"
• cluster - a group of areas - used for bots to more efficiently make their decisions - if they are too large the bots take up more cpu than necessary which will slow down the map - sometimes quite noticeably - a good goal is to have about 400 areas per cluster - bspc creates clusters automatically - but does not necessarily create them efficiently
• clusterportal - a 6-sided brush with the clusterportal texture applied to all sides - this is used to manually create clusters during the bspc process
• -optimize - the key you should always use to run bspc to create as small an .aas file as possible
• bot_testclusters 1 - console command that allows you to move around in map and see where clusters are located (and whether manual clusterportalization actually worked)
• bspc.log - the log file usually located in /Quake III Arena/ produced after bspc is run - details the number and size of clusters

Step 1 - square off everything: botclip OR playerclip OR fullclip
Some of the most significant gains in making bots run smother is to clip as much of your map as possible, especially in large open areas.  That is, brush planes are the source for creating areas in bspc - thus you want to "trick" bspc into thinking the map is smoother (less complex) than it actually is visually in-game.   In the case of objects inside the map, you cannot simply put clip in front of an object, the clip should surround the object.  Some good rules of thumb are:

• remember to clip axially - this means at 90 degree angles - this means boxes and rectangles which are straight up and down
• anything that is a set to contents detail should often be surrounded by a clipbrush
• models and some prefabs should usually be clipped since they have complex geometry
• anything that will not be accessed by players or bots should be clipped - this includes putting in a "false clip ceiling" since the sky is usually much higher than where players and bots can actually access
• rough surfaces - clip these with botclip so players can still walk on or beside these clipped objects - this could include terrain surface (but remember you don't want bots walking on air too much) (see figure 1)
• any complex geometry that is mostly visual (e.g. complex columns, light fixtures, complex trim)
• read the tutorial here

Step 2 - manually create area clusters: clusterportals
There is much to know about clusterportals and the rules for using them.  You should go here and read the "step two" there carefully.  They are placed somewhat like areaportals but the good news is that clusterportals do NOT break up brushes in the vis calculations like say a hint brush portal.  You have to seal off part of the map with your clusterportal brush - e.g. all the windows and doors in a building (even if they have glass already) to seal off the building.  The full list of rules for applying clusterportals is here but some key ones are:

• clusterportals must touch on all sides any of: structural brushes, playerclip brushes, botclip brushes.
• clusterportals should run parallel to the z axis, that is, only straight up and down not horizontil (e.g. within a hole in a floor)
• clusterportals need to by symmetrical such that both in-game faces of the portal are exactly the same shape - thus they cannot touch an angled clip or structural brush - that is, the clip or structural brushes that surround the areaportal brush cannot be angled on the x axis or the y axis (see figure 3)
• clusterportal brushes cannot have anything sticking through them - this includes train entities and teleporters that would move between the clusters
• clusterportals should not be more than about 32 units thick
• place clusterportals so the map is cut up into about 400 reachablility areas per cluster

Thus, place clusterportal brushes in your map to seal off areas according to the above rules.  Clipping and placing clusterportals in doorways, windows, and hallway entrances may be all you need to do - a relatively simple step to add to the speed of you map!  If you have large open areas though this may not be enough -  read step 3.

Step 3 breaking up large area clusters - combining botclip and clusterportals
Maps with large open areas, like terrain, make for additional challenges - but these challenges are realively easy to resolve with some creative brushwork.  Essentially you create a grid of large clusterportal brushes between botclip "posts/girders".  The basic idea is shown in figure 4 with cluster 1 separated from cluster 2 by a box of clusterportal brushes which meet at botclip posts/girders - note that all these brushes go from "floor" to "ceiling" sealing off the clusters entirely.  Since the botclip posts are relatively small, gameplay is not effected for the bots, they simply walk and shoot around the posts/girders.

figure 4

Consider an example where you simply need to split up a large open area that creates a very large single cluster, into two relatively even sized clusters.  It is actually much simpler to bisect (crosscut) the cluster with a single clusterportal than to put a box in the middle.  I have created a simple map with an undulating patchmesh floor - this creates a lot of areas fast even without any other brushes in the map.  We will cut the map in half with a clusterportal as in figures 5 and 6.  Just to be safe, place some botclip posts on the sides similar to figure 4, but have them butt up against the side sky brushes in this case (would "flush" be a better word?).  Also notice I have created a "false ceiling" with botclip.  While you may want a tall skybox for visual elements and so people don't leave the map in spectator mode you should put a false ceiling in to cut down the size of the areas and clusters (remember they are 3-dimensional).  The botclip on the floor is placed between two patch meshes and over laps them by 8 units each - thus bots will appear to walk on air here but this is a relatively narrow and thin brush and the effect will not be noticeable when playing the bots.

figure 5

figure 6

Step 4 checking your manual clusterportalization: bspc.log (in /Quake III Arena/)
There are at least three things you will want to check:

1. Are there areas in the map that appear solid to bots in game that should not (this is bad)?
2. Did your clusterportals actually work?
3. How much did your working clusterportals reduce bot CPU usage?

• enter the game and run your map with bot_testclusters 1 (pull down the console and type this) - this tells you which cluster you are standing in - thus in figure 7 the player is in cluster 1 and in figure 8 the player is in cluster 2 (green box upper left)- the clusterportal is working!  As you walk around watch for the upper left message to turn red - if it does it means a brush in the area is creating a solid brush for bots - that is, they will not walk there - so you will want to replace the brush.

• read the bspc.log file (I have renamed the bspc.log file and included it in the mapfile) - that is, run bspc before you insert the clusterportals, rename the bspc.log file after you run it, then run bspc again after you have inserted the clusterportal(s) - go to the bottom of the file and you will see the section that lists the clusters and the number of reachability areas in each cluster - it also lists the CPU usage.  For example here is the before and after for the mapfile I included (this is only a section of the whole output):

After inserting the clusterportal in figures 5 and 6:
...cluster 1 has 123 reachability areas
cluster 2 has 136 reachability areas
   259 total reachability areas
109422 AAS memory/CPU usage (the lower the better)
AAS data optimized.
writing C:\Games\Quake III Arena\baseq3\maps\clusterportal.aas...

Notice that:

• there are now two clusters
• each clusters has roughly the same number of reachability areas (123, and 126 - 400 max should be your goal)
• the memory/CPU usage is roughly halved from 237726 to 109422
• the aas is optimized (that is, bspc was run with the -optimize key)

Contact - please report any errors or omissions
[email protected]