HowTo/Solve Blender Modelling Problems

Using Blender for Making Trainz Content

The Blender 3D modelling software is ideal for making content for Trainz and a huge amount of 3rd party add-ons, tutorials and documentation exists on the web. Examples include the main Blender site, BlenderNation and Blender Artists. A search of the web will reveal many others.

Help specifically for Trainz purposes is harder to find. There are some "How/Tos" on this site, some on WiKi Books, Ian Cayden's Blender Notes and Paul Hobbs' Tutorials . Paul Hobbs' tutorial still recommends Blender 2.49b although a later revision may be available soon.

Purpose

This page contains answers to frequently asked questions (FAQ) relating specifically to Trainz modelling and should be useful for both beginner and more experienced creators. The Trainz Blender community is encouraged to add their own submissions.

Exporting

Surfaceless Polygons

Symptom: The exporter log contains a message like this:

 15:33:10 WARNING: surfaceless Polygon(s) in Object "rdc12349end.001", Mesh "Cube.097" detected
 15:33:10 INFO:    Vertices of surfaceless Polygon(s) gathered in Vertex Group "ERROR_surfaceless_Polygons"

Comment: Surfaceless polygons (aka faceless faces) are polygons which cannot form a plane (face) between the polygons vertices. This problem often arises when an extrusion is initiated but not completed. In this case two or more vertices may occupy the same location. Here is another explanation by Torsten:

Let's call the corner points (vertices) of a triangle (the simplest possible face) A, B and C. As long as all three corners have different locations they define a plane, a two dimensional object. The part of the plane inside all three vertices is what we call surface or face. So far for the "good" case. Now the "bad" case. Imagine point B moves to the location of A: suddenly we can no longer tell if what we see is a triangle or a line. We can no longer define a plane because all three vertices now only form a line (of course a line with three points instead the necessary two points). As our triangle (aka polygon) now has no surface (we need a plane -> 2D and have a line -> 1D) we have created a "surfaceless polygon".

The exporter itself needs a plane because for every exported triangle Trainz want to know its normal (to calculate the color of that face for example), and a 3D normal needs a 2D plane. Try to calculate the normal for a surfaceless polygon will end in a division by zero.

Solution: This can be cured by selecting the mesh and using the "Remove doubles" command. You can identify the problem vertices by selecting the problem mesh and then going into the Properties Browser and the Object Data (the triangle) tab. There is a section called Vertex Groups and the newly created vertex group with the problem should be listed. There are options to highlight the vertices in the group.

Comment: Another cause of surfaceless polygons is when there are two edges that seem to join, but where the edge on one side does not have the same number of vertices as the edge on the other. As an example, if one starts with the default Blender cube, and extrudes the top face of the cube to create a first story. and extrudes the top face again to create a second story, the result is a stack of 3 "cubes". Now, if one decides to add a door, or a window, in one face of the center cube of the stack by deleting the center face one side, and extrudes both vertical edges towards the center, and then makes a face from the two resulting extruded edges, one has created two surfaceless polygons, one from the four vertices that lie in a line at the top of the door, and one from the four vertices which lie at the bottom.

Solution: A modificaton of the work flow. If one decides to add a opening, instead of deleting the face, and creating the opening by extruding edges or vertices, either make loop cuts around the object as needed, and delete the necessary face, or subdivide the face

See Also: This Trainz forum thread