Almost all lighting billboards come from OBJs, via named lights or custom lights.
They are usually subject to level of detail (LOD). However, there are some exceptions.
Philosophy:
- Authors know better than X-Plane when an OBJ should disappear – it’s a subjective thing. X-Plane always honors ATTR_LOD for triangles.
- X-Plane knows better than authors when a light should disappear – since X-Plane knows how those abstract light params are rendered. X-Plane may ignore LOD. Usually this involves light being drawn for a longer distance, in cases where there is no perf hit in the rendering enigne. This is almost always desirable for authors.
Guidelines:
- Replicate your lights through all LODs with the SAME exact values.
- You can drop a light in far LOD but don’t add one.
Notes on implementation:
- X-Plane may draw your light for longer than you want – calc will be based on light’s actual appearance.
- X-Plane won’t double-draw extended-LOD lights when repeated in two LODs. Not a problem!
- Don’t add lights in far LOD – X-Plane may not be able to accurately do this effect if it is tampering with LOD!
- If your last LOD is light only, X-Plane can handle this VERY efficiently. So often there is penalty for huge final LOD for a named light that is geo only.