Volumes are invisible areas that are created to help the game developers perform a certain function. They are used in conjunction with the objects in the level to perform a specific purpose. Volumes are commonly used to set boundaries that are intended to prevent players from gaining access to trigger events in the game, or use the Lightmass Importance Volume to change how light is calculated within an area in the map as in Chapter 2, Creating Your First Level.
Here's a list of the different types of volumes that can be customized and used in Unreal Engine 4. But feel free to quickly browse through each of the volumes here for now, and revisit them later when we start learning how to use them later in the book. For this chapter, you may focus your attention first on the Trigger Volume, as we will be using that in the later examples of this chapter.
The Blocking Volume can be used to prevent players/characters/game objects from entering a certain area of the map. It is quite similar to collision hull which we have described earlier and can be used in place of Static Mesh collision hull, as they are simpler in shapes (block shapes), hence easier to calculate the response of the collision. These volumes also have the ability to detect which objects overlap with themselves quickly.
An example of the usage of the Blocking Volume is to prevent the player from walking across a row of low bushes. In this case, since the bushes are rather irregularly shaped but are roughly forming a straight line, like a hedge, an invisible Blocking Volume would be a very good way of preventing the player from crossing the bushes.
The following screenshot shows the properties for the Blocking Volume. We can change the shape and size of the volume under Brush Settings. Collision events and triggers other events using Blueprint. This is pretty much the basic configuration we will get for all other volumes too.
The Camera Blocking Volume works in the same way as the Blocking Volume but it is used specifically to block cameras. It is useful when you want to limit the player from exploring with the camera beyond a certain range.
The Trigger Volume is probably one of the most used volumes. This is also the volume which we would be using to create events for the game level that we have been working on. As the name implies, upon entering this volume, we can trigger events, and via Blueprint, we can create a variety of events for our game, such as moving an elevator or spawning NPCs.
The Nav Mesh Bounds Volume is used to indicate the space in which NPCs are able to freely navigate around. NPCs could be enemies in the game who need some sort of path finding method to get around the level on their own. This Nav Mesh Bounds Volume will set up the area in the game that they are able to walk through. This is important as there could be obstacles such as bridges that they will need to use to in order get across to the other side (instead of walking straight into the river and possibly drowning).
The Physics Volume is used to create areas in which the physics properties of the player/objects in the level change. An example of this would be altering the gravity within a space ship only when it reaches the orbit. When the gravity is changed in these areas, the player starts to move slower and float in the space ship. We can then turn this volume off when the ship comes back to earth. The following screenshot shows the additional settings we get from the Physics Volume:
The Pain Causing Volume is a very specialized volume used to create damage to the players upon entry. It is a "milder" version of the Kill Z Volume. Reduction of health and the amount of damage per second are customizable, according to your game needs. The following screenshot shows the properties you can adjust to control how much pain to inflict on the player:
We kill the player when it enters the Kill Z Volume. This is a very drastic volume that kills the player immediately. An example of its usage is to kill the player immediately when the player falls off a high building. The following screenshot shows the properties of Kill Z Volume to determine the point at which the player is killed:
The Level Streaming Volume is used to display the levels when you are within the volume. It generally fills the entire space where you want the level to be loaded. The reason we need to stream levels is to give players an illusion that we have a large open game level, when in fact the level is broken up into chunks for more efficient rendering. The following screenshot shows the properties that can be configured for the Level Streaming Volume:
The Cull Distance Volume allows objects to be culled in the volume. The definition of cull is to select from a group. The Cull Distance Volume is used to select objects in the volume that need to disappear (or not rendered) based on the distance away from the camera. Tiny objects that are far away from the camera cannot be seen visibly. These objects can be culled if the camera is too far away from those objects. Using the Cull Distance Volume, you would be able to decide upon the distance and size of objects, which you want to cull within a fixed space. This can greatly improve performance of your game when used effectively.
This might seem very similar to the idea of occlusion. Occlusion is implemented by selecting object by object, when it is not rendered on screen. These are normally used for larger objects in the scene. Cull Distance Volume can be used over a large area of space and using conditions to specify whether or not the objects are rendered.
The following screenshot shows the configuration settings that are available to the Cull Distance Volume:
The Audio Volume is used to mimic real ambient sound changes when one transits from one place to another, especially when transiting to and from very different environments, such as walking into a clock shop from a busy street, or walking in and out of a restaurant with a live band playing in the background.
The volume is placed surrounding the boundaries of one of the areas creating an artificial border dividing the spaces into interior and exterior. With this artificially created boundary and settings that come with this Audio Volume, sound artists are able to configure how sounds are played during this transition.
The PostProcess Volume affects the overall scene using post-processing techniques. Post-processing effects include Bloom effects, Anti-Aliasing, and Depth of Field.
We have used Lightmass Importance Volume in Chapter 2, Creating Your First Level, to focus the light on the section of the map that has the objects in. The size of the volume should encompass your entire level.