by Jason “despain” Perry
Understanding Common Events
Today we’re going to look at a part of RPG Maker VX Ace that a lot of new users find confusing or intimidating. In reality, common events are pretty straightforward—though their position in the database might leave the opposite impression. A lot of people—maybe even yourself—overlook common events. The purpose of this article is to explain the functions of common events and encourage new RPG Maker users to explore the multitude of options that common events allow.
What is a Common Event?
Simply put, a common event is an event that can run on any map in your game. A better name for them might have been “global events”.
Common events do not have graphics or physical locations—you don’t make a character with a common event. Instead, a common event is all about behind-the-scenes processing. Common events are perfect for global “systems” that add functions to the game. Common events can run in the background of your game, they can be triggered by switches, or they can be called from other events.
Before we dive into some examples, let’s look at the common event tab in the database:
The tab is dominated by a “contents” pane—this is something that should be familiar. It works just like any other event you create on a map. Every event command is accessible here—use event commands to tell a common event what to do. In that respect, common events are easy to use. If you have an understanding of the event commands, there’s very little to common events that will seem new to you.
Along the left side of the tab is a listing of all the common events in your game—an RPG Maker VX Ace project can have up to 999 common events. That’s quite a lot! Be sure to give each common event a useful and identifying name.
How do I use Common Events?
At the top of the tab, there’s a section labeled “General Settings”.
There are only three fields here, and one of them—the name—needs to explanation.There are three main ways to activate a common event.
If you understand regular event triggers, you know that Autorun events prevent player input while running. In regular events, these are mostly used for cutscenes. A common event with an Autorun trigger will run in a continuous loop as long as its “Condition Switch” is turned on.
Let’s say that you have an event on one of your maps that turn on a switch—if that switch is assigned to a common event with an Autorun trigger, the common event will see that the switch has been turned on and will “kick in” right away.
To turn the common event off again, you’d need to turn the switch back off. Because the Autorun trigger prevents the player from moving or other events from processing, you’ll usually turn the switch off within the common event itself.
Parallel process is a lot like Autorun, except that it runs in the background of the game, allowing the player to move and interact with other events. In other words, it runs parallel to the rest of your game.
Just like Autorun common events, a Parallel Process common event will repeatedly loop as long as its condition switch is on. This can be useful when used in conjunction with Conditional Branches, as it can allow you to create events that trigger automatically when certain conditions are met, regardless of where the player is in the game.
Word of warning: Be careful with too many Parallel Processes going on at once, as it can potentially cause lag on slower computers. You can eliminate some of this by using wait commands, or by using labels to shorten and clean up loops. RPG Maker VX Ace is powerful enough to run multiple Parallel Process events and common events at once, but it is worth keeping in mind.
You’ll notice the event command “Call Common Event” in the Flow Control category. You can use this command to call a common event that doesn’t use a switch trigger. Common events with a trigger of “none” can still be accessed with the “Call Common Event” command.
When you call a common event from another event, imagine that the contents of the common event will be plugged into that event. The “Call Common Event” command within a regular event will be read in-game as the contents of the common event.
For example: When working with common events, you’ll notice that “this event” (in the “Set Move Route” command, for example) is a selectable choice. This won’t work in a common event that is triggered by a switch—because there is no physical event assigned to the common event. However, when you use this command within another event via “Call Common Event”, that information transfers to the event that is calling it, and the common event can move “this event” without problem.
What can they be used for?
Common events can be used for pretty much anything! When you understand common events, a lot of potential opens up for you as a developer. You have greater control over your game in an efficient way.
Let’s take a look at an example of two common events.
This is a trick that can save you a lot of time and headache. Imagine that you have an event that will appear a lot of times in your game—maybe a door or a treasure chest. You’ve made the event, but maybe you are using a placeholder sound effect or animation. Put your working version in a common event, and use the “Call Common Event” command in each one of these events on the map. That way, when it’s time to finalize the event later on, you only need to edit the common event—boom, all of the events in the map have been instantly updated.
Here’s another example of something a little more complicated:
Say that you want a day/night cycle in your game. You can create a Parallel Process common event that controls this. With some conditional branches, variables, and wait commands, your common event can constantly keep track of the game world’s time in the background. You can tint your screen for nighttime from the common event, and tint it back when the sun rises. By turning on switches within this common event, other events on your map can act differently depending on the time of day.
Conclusion
Common events are a very powerful feature of RPG Maker VX Ace. We’ve covered the basics in this article, and you should be ready to experiment on your own! If you run into any problems, ask for some help on the Official Forums.
Use your imagination. And have fun. 
Jason “despain” Perry has been using RPG Maker for over a decade, and in that time his articles, tutorials, and graphical resources have helped countless RPG Maker users on community forums. He currently runs the website finalbossblues.com, where he co-hosts an RPG Maker podcast and regularly posts new articles and tutorials.
How it works: Parallel Process triggers work similar to autorun triggers in that they start whenever the conditions are met, but instead of stopping player action, they run in the background allowing the player character to continue on while the process is working. They also, as with Autorun Triggered events, repeat indefinitely as long as conditions for them are met.
