LODs -- some how-tos

Naming LODs
There is a standard way to name LODs. By the way, the FS2004 GMAX SDK tutorial uses Dummy Objects to link LODs, but to me this is an extra complication, and unnecessary. The naming convention remains the same, though, and straying from this can cause problems.

The format is: objectname_LOD_###, where ### is a 3 digit LOD number. So our fence may have these LODS:
fence_LOD_010
fence_LOD_100
fence_LOD_600

Don't forget both the underscores, and the numbers always have 3 digits.

My method requires that each LOD of your completed model be one object.
This is because each LOD has the same object name, just a different LOD suffix. You may have to combine a number of objects into one within GMAX. The simplest way is to Attach every part of your object.

Before we get ahead of ourselves, though, we need to have a little look at how we are going to manage our LODs. What we want to finish with is one separate object for each LOD. If we need to combine bits and pieces to get this one object, we don't want to get mixed up with what object belongs to which LOD. Working with LODs is a good time to get to know how to make bits disappear so they don't get in the way.

The Display rollout offers a huge range of tools to change what is displayed. The tools I use most here include:
Hide Selected: this can make a finished object disappear.
Hide Unselected: Just leave the one thing we are working on, to simplify the display.
Hide by Hit: make anything that gets between me and the object I want to work on disappear by clicking on it; and of course:
Unhide All: makes everything come back.
Hide by Name is useful for those who organise their models to a large extent -- with well-named objects -- such as a prefix for multi-object models -- you can just choose from the dropdown object list.
Unhide by Name is just as useful, letting us switch LODs in and out of the display.

Have a wee play with the Display rollout if you haven't really made use of it before./p> Ok, before I get back to the subject of combining objects, I'll quickly outline one method using the tools of the Display rollout.

If I make a complex object first, such as a terminal building, before I even think about LODs, I need to duplicate the terminal to have the starting point for our reduced-polygon LOD. To do this, I might:

Select all the objects which make up the terminal, and duplicate them. Without changing the selection, I group the selection and call it LOD1.

Grouping is a handy tool for modelling, but just be aware that a Group isn't recognised by the GMAX exporter, or the simulator. Grouping is not enough to combine multiple objects into one. However, it is a good way to bind objects together temporarily.

Now I make it disappear, by using Hide Selected from the Display rollout.

Now I have a copy of all the objects which make up the terminal. I repeat the process for each LOD I require. If I only want two LODs, I'm finished, though.

Now I can reduce the complexity of the objects remaining, by:
Deleting some frilly bits;
Removing some polygons;
Reducing the number of sides to cylinders etc; (that's why we try to leave the objects as their original geometry. It's easier to reduce the number of sided from a cylinder by clicking a box, rather than doing it manually to a polygon.)
Combining vertices by welding etc.

During this process, we can begin welding the object together. I prefer Attach to do this. The easiest way to access the Attach tool is to right-click an Editable Mesh or Editable Polygon.

Note: there is a difference with the attach tool depending on whether you have an editable mesh or a polygon. With a mesh, the tool becomes Attach, and you click on the objects you wish to attach. With a polygon, the tool becomes Attach List, where you choose the objects from a list.

When we get the object fully optimised, we can Attach everything, rename it with the correct LOD name (just guess a LOD value until you can figure this out later, if you wish.)

Now make it disappear. Magic! (sorry, I meant Display Rollout -- hide Selected.)

Although you could use this LOD to create the starting point for the next. It depends on whether you consider it easier to reduce it further from the total, finished and attached object, or the bits which it was originally created from.

Now, if we've finished making reduced-polygon LODs, bring back the original -- Unhide by Name -- LOD1, which was our group. Select the group, and hide everything else -- Hide Unselected.

Now ungroup the LOD1 group, we've finished with grouping, remember it was just a temporary measure, and has no real use in making flghtsim scenery!

Now we can Attach everything. The easiest way is to select an object which is already an Editable Polygon, or convert an object to an Editable Polygon. Right-click the object, choose Attach List, Select All from the list and OK! We've finished. Now give it a proper LOD name and value.

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