Lighting Level of Detail

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.
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