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# Unreal Geometry

work in progress

EntropicLqd: Who is this work in progress by?

Everything you see in the Unreal World is generated from wireframe objects (called brushes in mapper speak), [Static Meshes]?, and Actors?. Static meshes are not used by Unreal Tournament.

The term generated in the above paragraph was used because what you actually see in the world is a render of a BSP tree. The wireframe brushes are used to generate the surfaces in the world which you as a mapper cover with textures. These surfaces are placed into a BSP tree for efficient and speedy display. The static meshes in the world

One of the common misconceptions when using the Unreal Editor is that the brushes and static meshes are directly tied to the 3D view of the world. While moving static meshes around will cause a corresponding change in the 3D view moving the wireframe brushes around will not. This is because the surfaces generated by the wireframe meshes are being rendered from the BSP tree. In order to see a change in the 3D view when a wireframe brush is used the Geometry must be rebuilt. This rebuilds the BSP tree which in turn causes the 3D view to be updated.

- The basics of how the world is put together: brush wireframes & actors. UEd creates the 3d world from the brushes.: see also Unreal World
- ... and surfaces != brushes. Common n00b mistake to refer to surfaces as brushes, and thence the confusion of why moving a brush doesn't move a surface.
- the 2nd layer: actors.
- why each time you click on a primitive, you get a new shape replacing the old one
- the fact that geomtery in the 3D view is not permanent – why it doesn't change when you move corresponding brushes (quake mappers particularly will be confused by this) and v. quick intro to rebuilding.

common beginner confusions:

- using "hollow" option on the Cube and Cylinder builders to make rooms – you're building additively, and in Unreal that means you're thinking the wrong way.
- delete a brush: the world stays the same. The surfaces that were tied to that brush still exist. Operations which depend on the BSP will treat that brush as still existing, eg Intersection.

Part 2 will probably be [Unreal Actors]?

things for part 2:

actors can be moved, settings changed etc without needing to rebuild anything.

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