Editing Doom engine (section)

===Things (sprites)===
Each sector within the level has a linked list of things stored in that sector. As each sector is drawn the sprites are placed into a list of sprites to be drawn. If not within the field of view these are ignored.

The edges of sprites are clipped by checking the list of segs previously drawn. Sprites in ''Doom'' are stored in the same column based format as the walls are, which again is useful for the renderer. The same functions which are used to draw walls are used to draw sprites as well.

While subsectors are guaranteed to be in order, the sprites within them are not. ''Doom'' stores a list of sprites to be drawn ("vissprites") and sorts the list before rendering. Far away sprites are drawn before close ones. This causes some overdraw but usually this is negligible.

There is a final issue of middle textures on 2-sided lines, used in transparent bars for example. These are mixed in and drawn with the sprites at the end of the rendering process, rather than with the other walls.