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Half life 2/ Counter Strike: Source bot Charlie Cross CIS 488 2-14-05.

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Presentation on theme: "Half life 2/ Counter Strike: Source bot Charlie Cross CIS 488 2-14-05."— Presentation transcript:

1 Half life 2/ Counter Strike: Source bot Charlie Cross CIS 488 2-14-05

2 Background Counter Strike is a multiplayer modification for Half life, released in June of 1999. Valve software hired the counterstrike team and ported Counter Strike to their new Source engine. Outsourced a spin off single player product- Counter Strike: Condition Zero. Ended up being finished at Turtle Rock Studios.

3 Background (2) Turtle Rock developed artificial intelligence for condition zero. AI was ported to CS: Source last month.

4 AI features: Navigates map using automated systems (waypoints) combined with human teaching (navigation meshes). Communicates with human players, telling them where enemies are located. Follows human instructions (e.g. “follow me”, or “team fall back”) Selects best weapon for tactical situation. Avoids tactically disadvantageous situations. Conveys range of emotion-driven behaviors. Rushes aggressively when winning or retreats when outnumbered.

5 Navigation Meshes

6 Navigation Use of nav meshes allows bots to be less predictable and to use less structured behavior the way humans do. A* pathfinding. Uses reactive obstacle avoidance (like the quake bots) To avoid crashing into walls and other objects. Monitor’s average velocity to detect when the bot is “stuck”, then uses a “random wiggle” to try to jerk free. (I have never seen this happen)

7 Using the tools to build paths. (Source: Mike Booth’s presentation at GDC)

8 Using and viewing the environment Nav meshes include “hiding spots” that are labeled by the programmer. When retreating or “camping” the bot will find a hiding spot to ambush the opponent. Looks around smoothly and avoid jerky movements. Looks around corners and checks openings.

9 Tactics

10 Tactics and Bot emotions Nav Areas hold a danger value. Increased danger means increased cost (A*) This forces bots to change routes. Danger values are increased when bad things happen (such as team mates dying) Morale determines level of aggression. High morale: Bot is on winning team, bot is killing enemies. Low morale: Bot is on losing team, bot is killed, hurt.

11 Combat and Weapon selection Since it is a rule based system, there are an elaborate collection of rules to determine combat actions. Examples: –Using the appropriate weapon for the range: (Sniper rifles if enemy is far, pistol if close.) –Aiming for the head. –How to use grenades effectively (flush out enemies if attacking, slow them down if defending)

12 Team awareness Follows the leader (you) Communicates enemy locations Uses stealth (sneaking slowly to reduce noise) when heavily outnumbered Avoids stupid problems like shooting teammates, (will yell at you if you do).

13 Effects on Gameplay Why make a bot for a multi-player game? –Some servers don’t have a lot of players on them. Bots can fill in the gaps to make a full team. –Lousy internet connection wont prevent players from enjoying game. –Bots don’t accuse you of cheating when you kick their ass.

14 Strengths and weaknesses Strengths: –Bot is almost convincingly human. –Bot difficulty is scalable to match different skill levels. –Bots don’t change flow of game, they are just like other players. Weaknesses –Bots can see perfectly in dark areas. –Bots often prioritize killing enemies over completing mission objectives. (Then again, so do most human players.)

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