INTERIOR LODS

For each type of aircraft, the way in which the cockpit - and the cabin if required - merge into the exterior airframe will be handled slightly differently depending on the actual geometry of the aircraft. For example, if the cockpit windows are very small then you will not be able to see much from outside of the plane when you are at LOD x1. Conversely, you will be able to see much more of the interior at LOD x1 if the cockpit is very exposed. As such it is important to consider how much of the interior you will see when the plane transitions through the LODs, and adjust the details and tris used accordingly.

 

 

Cockpit LOD Considerations

For most planes the cockpit is modelled in a separate file which is merged at runtime with the exterior. The cockpit, like the airframe, has a top LOD x0 which is used for close ups of the cockpit controls and when the user is actually inside the cockpit. The next LOD down would be LOD x1, which has it's geometry reduced by approximately 50% and will be used when the camera is outside the aircraft and viewing the inside cockpit through the windows. This means that it's extremely important that the window frames for the exterior and interior LODs line up accurately as the LODS change, keeping in mind that they may not be on the same LOD. Note too that large cockpit elements that are animated, should also animate through the LODs, such as the yoke, throttle, and anything visible from the outside, however the buttons and small dials will not need to animate.

 

The table below shows the approximate correlation between exterior and interior LODs:

 

Cockpit LOD	Exterior LOD
x0 (Interior View)	x0
x1 (First LOD visible from Exterior)	x0
x2	x1
x3	x2
x4	x3
x5	x4
(none)	x5, x6

 

As you can see, the cockpit does not have any LODs to match exterior x5/x6 as these are too small on screen to be noticeable. On smaller aircraft it may be that you don't even need an interior LOD from LOD x3 onwards.

 

To give an example, we'll look at the Boeing 747. This aircraft is interesting because it illustrates the fact that often the largest aircraft have the smallest windows, and as such they can get away with a much lower resolution cockpit LOD from x2 upwards.

What that means for this aircraft is that the cockpit LODs from x2 onwards are there purely to provide silhouette detail and "depth" to the user viewing the aircraft from outside. The mesh resolution drop will therefore be significant from X1 to X2 if the windows are small, and equally significant from X2 to X3 as all of the details are removed from the interior. The images below show the visual results of this resolution drop for the 747 cockpit model:

Cockpit LODx0

 

Cockpit LODx1

 

Cockpit LODx2

 

Cockpit LODx3

 

As mentioned already, smaller planes, or those with much more exposed interiors will carry more detail down through the LODs so they maintain sufficient detail when viewed from a distance.