Introduction | Command Line & Usage | Detail Brushes | Direct & Face Mode | Extrusions

Direct Mode
OBJ2MAP will attempt to convert a mesh group without a name flag using "direct" mode. Simply put, every face in the mesh group is converted into a clipping plane. Direct mode only works on closed, convex volumes. It is really easy to create invalid geometry, so direct mode's usefulness is limited, but it can be helpful for creating walls, wedges, cylinders, or for otherwise difficult vertex manipulations. Direct mode can also facilitate the creation of complex arrays of simple shapes (like steps for a spiral staircase) since most 3D packages have far more sophisticated cloning/array tools than the average Quake Map editing program.

It's important to realize that a brush clipping plane in a MAP file is always represented as three coplanar points. OBJ2MAP will discard redundant polygons and points that lie on the same plane (only the first three points of a quad are used for example). You can use this to your advantage in certain situations, like capping highly subdivided cylinders with a single triangle.
All the mesh groups pictured to the left will result in a solid cuboid brush when converted in Direct Mode. Each polygon is converted into an infinite plane, redundant planes are discarded, and the volume contained within all the intersections is the brush you'll end up with.

An important thing to note is that the facet normal direction must face outward or the winding order will be incorrect, resulting in an invalid brush.

Face Mode
Flagging a mesh group's name with _FAC_ will tell OBJ2MAP to create a thin pyramidal brush from each polygon. Face mode can be used to convert extremely complicated geometry into brushes, but it comes at a cost (mainly high polygon counts). Used sparingly, face mode can help add details to a map that are otherwise impossible, but it should only be used when all other options fail. Heightmap or Axial extrusion methods may often provide a better alternative. The -foffset command line option can be used to globally adjust the thickness of the pyramidal brushes. The default -foffset value is 4, and it's usually best to keep it low since the apexes of neighboring polygons can easily "pierce" one another. Setting it too low however, can result in a bad conversion due to a loss of precision when the apex coordinate is rounded off.

Important: Face mode groups the resulting brushes into an am_detail entity flagged as "Solid" and places an ignore texture on the "insides" - the insides being all faces except the original polygon. eQBSP uses a horrid hack for ignore textures that exploits a bug in GLQuake, causing the surface to be invisible. Unfortunately this doesn't work with software rendered Quake, where the surface is rendered as a generic "checkerboard". You should therefore avoid using face mode or re-texture the brushes if you want maximum compatibility software Quake (at the cost of rendering 3 times as many polygons).

Notes:
Face mode is much more reliable when all polygons in the mesh group are triangles.
Using face mode "inside-out" can produce interesting effects, but it will require re-texturing to ensure that all faces will be visible in Quake.
"Ranger Monument"
(Q3A model converted using face mode)
Just because you can do something, doesn't mean you should!

Introduction | Command Line & Usage | Detail Brushes | Direct & Face Mode | Extrusions