Rail Sim LOD export

Not a problem, just send over the file – examples are always the best way to see what is going on.

LODs and 3DC
==================

Rail sim uses a name prefix system to display parts at certain distances.
The developer documents (4.03 General Guidelines, p6) explains the concept for MAX users.
For 3DC, the node name coresponds to the Group name in the 3DC hierarchy.

Now the 3DC exporter goes a stage further and tries to be a bit clever where node names are concerned.

1. If there is no ‘n_dddd_’ prefix to the group name, it will automatically add a prefix depending on the export options selected.

2. If a name is defined in the ‘Rail Sim’ custom group field (shown in the Group or Object properties page in 3DC), that will be used instead. Again a prefix is added if none is found.

The exporter plugin will also only export the current group and all groups under the current group.

There are 2 exceptions to this:
– If no group is selected, it scans for a group called Main and exports that.
– If Custom LOD export is selected, sibling groups are scanned for the same name but with a .NNN suffix (more later)

Export Options

1. No LODs

This is a bit of a misnomer, it really means you can specify lods in the group names. You just need to be careful to make sure the group names correspond exactly.

Any prefix added will always be 1_1000_
e.g.
[pre class=’ip-ubbcode-code-pre’]
Scene
+— Main
+—- 1_0100_Detail
DObject1
DObject2
+—- 2_0500_Detail
D2Object1
D2Object2
+—- OtherGroup
XObject1
XObject2
MObject1
MObject2
[/pre]

If MObject1 or 2 are selected, then the model will show these and the objects in ‘OtherGroup’ up to 1000m, the DObject* parts up to 100m and the D2Object* parts from 100 to 500m

Exports as:
1_1000_Main
1_0100_Detail
2_0500_Detail
1_1000_OtherGroup

2. Automatic LOD

This option looks at the size of the bounding boxes of Objects in 3DC.

All objects are shown up to 100m
Objects with any 2 dimensions of 0.25m or less are not shown from 100-400m
Objects with any 2 dimensions of 0.83m or less are not shown over 400m

With this option you do do not have as much control over the group naming. If you have used the n_dddd_ prefix it will be removed and re-calculated by the exporter.

The trick with this option is to keep small parts as separate objects. merge objects that you want to keep showing for longer.

e.g.
[pre class=’ip-ubbcode-code-pre’]
Scene
+— Main
+—- 1_100_Detail
DObject1*
DObject2**
+—- OtherGroup
XObject1*
XObject2*
MObject1*
MObject2
[/pre]
In this case if the objects marked with * have 2 dimensions of .25m or less and ** have 2 dimensions or .83m the groups exported are
1_0100_Main
1_0100_Detail
1_0100_OtherGroup
2_0400_Main (only 1 object)
2_0400_Detail (only 1 object)
3_1000_Main

With most models this should be the preferred export option.

3. Custom LODs

In this case, LOD’s are built as individual models at the same level in the 3DC hierarchy

If an object in the ‘Main’ group is selected on export and custom LOD is selected, the exporter looks for any sibling groups to Main with a number at the end

e.g.
[pre class=’ip-ubbcode-code-pre’]
Scene
+— Main

+—- Detail
DObject1
DObject2
MObject1
MObject2

+— Main.200

+—- Detail
DObject1
DObject2
MObject1
MObject2
[/pre]
The Main.200 group does not have to be at the same position as Main, just the centre of the model needs to be the same (see my Building tutorial)
The objects in the two modelled LOD’s can be completely different e.g. Cylinders with fewer sides.

This example exports 2 LODs
1_0200_Main
1_0200_Detail
2_1000_Main
2_1000_Detail

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