Creating a Basic Level

These are the steps necessary to create a basic unreal level. It is a good idea for you to try to follow the steps here to find your way around the Editor.

BSP/CSG Geometry

Early versions of Unreal used something called BSP geometry as their primary method of creating 3D content. BSP stands for binary space partitioning and is a data structure used in graphics. However, the more accurate term for the type of geometry created by unreal is Constructive Solid Geometry or CSG for short. In any case if you are reading documentation for unreal, know that the terms are interchangeable.

The way that BSP geometry is constructed is quite different from constructing a mesh in say 3DS max. Instead of editing vertices/edges/faces, BSP geometry is typically created by adding and subtracting geometry from each other. You constantly think about the world as being made of either solid matter or empty space.

In older version of the unreal editor the world that you create starts off in additive space. That is, the world starts off solid and you carve out the shape of your world from this solid space. In the current version of UDK, the word starts off in subtractive space and you add geometry to it.

BSP geometry is typically used for building things that are big and non-detailed (such as walls and floors). For anything with any sort of detail static meshes are far better.

How to work with BSP Geometry

Building geometry with bsp involves working with brushes. Inside unreal ed, the type of brush (and in fact the type of actors as you will see later) can be identified by the colour of brush which can easily be seen in any of the orthographics views.

To create geometry

start with a builder brush to get the shape that you want. Now, since unreal typically starts off in additive space (ie empty space) what you need to do is add something solid to it. If you are building a purely indoor level, start by creating a giant block of solid that you can then carve your level into.

In any case the process of creating geometry with BSP is the same. Start by creating a builder brush. Standard shapes for a builder brush can be created by hitting any of the buttons on left under Brushes. If you left click the button a red brush outline will show up in the view ports. You can alter parameters for that brush (size, number of sides etc) by right clicking on the button instead. This will produce a dialog box that lets you set parameters. for the brush.

Hitting the "Build" button on the brush does not create any geometry, it simply builds the builder brush.

To create geometry, you will need to create an additive or subtractive brush from the builder brush. Now, since we are starting in additive space (ie all empty) you will need to "add" to it to create somethign solid. This can be done by hitting the "add" button under CSG.

Once you have something solid, if you wish to hollow it out, create a builder brush that fits into a block of solid, and position it in to place inside the solid. After this, hit intersect button (diagonally down to left of subtract) and then hit the subtract button.

The intersect button fixes the builder brush so that if any part of the brush is in additive space (ie any part of it is in hollow space) it will modify the brush so that the part of the brush that intersects with hollow space is removed. (the final builder brush is only the component that is inside the solid block). This will prevent subtracting from additive space (remove emptiness from emptiness) which can cause wierd visual artifacts. In general you should always hit intersect before subtract. Similarly you should always hit deintersect before you hit add. Deintersect is diagonally down and to right of add button.