Tonight I have been improving how ModelConverterX reads levels of detail from FS2004 MDL files. The LOD values are now calculated more accurately. Since I spend quite some time figuring out some details I had figured out last year already (but forgot since then), let me sum up my main findings about levels of detail:
- The LOD switching distance is determined by the object radius and the LOD value. For example a LOD value of 40 means that the object will switch when 2.5 times the radius of the object covers 40 pixels.
- The LOD value of the highest LOD is not relevant, since this LOD is never tested. So when you have an object with LOD_010, LOD_040 and LOD_100, it will display the same as that object with LOD_010, LOD_040 and LOD_200. For ModelConverterX this means it can not accurately read the highest LOD value, since it is not stored in the MDL. ModelConverterX will assume it is twice the LOD value below it.
- The radius of the object used for LOD calculations is a sphere fitting tightly around the object, so it is not the radius of the bounding box.
Do I understand correctly?
No, at LOD 40 the total size on screen is 2.5 times the radius. So if your object has a radius of 10 meter (20 meter diameter), than 25 meter covers 40 pixels.