Overview
A quick fix to remove haze polygons, mirage mountains etc.
How to remove haze polygons or mirage mountains
I have been frustrated by the sight of strange polygons that appear between mountains on cloudy or hazy days. The appearance of these mirage are not only distracting and can spoil a good screenshot, but actually interfere with VFR navigation as they can completely distort the landscape at the horizon making it difficult to spot recognisable features.
This is an example of the effect as seen from Tofino on a clear day with 40km visibility. There is a large flat grey polygon object lying across the mountain tops:
You may be familiar with the concept of tiles as a way a simulation program creates a 3d mesh landscape. What I did not know was that X-Plane also draws a 3d mesh planet model. This is important for high altitude flying as it gives definition to the terrain beyond the range at which the regular scenery mesh is drawn.
However, the distance at which this planet is drawn appears to be connected with the visibility parameter in the X Plane weather generation system. X Plane seems to draw the planet mesh at the edge of this visibility setting, and so on hazy days or in cloudy weather when the visibility can be reduced to relatively low distances (40km for example), X Plane draws the planet mesh quite close to the player’s point view. It is the planet mesh being drawn which causes the unsightly mirage in the mountains.
So what can be done?
One quick fix is ridiculously simple, but has some consequences which should be considered.
You can choose whether X Plane renders this planet or not.
Open the X-Plane.prf file (located in the preferences folder of your main X Plane installation) with a text editor (e.g. notepad++) and look for the following line, which should be near the bottom:
‘renopt_planet 1’
and change it to
‘renopt_planet 0’
….that’s it!
X-Plane will no longer render the planet and you will not see these polygon mirages anymore.
Here’s a before and after:
However, this will reduce the quality of scenery as observed from high altitude. So if you are flying big jets at 30,000 ft, you may decide the loss in terrain fidelity at long distance is not an improvement.
But if you are a GA flyer and spend most of your time at low level and very rarely see out to 160km distance (the max visibility weather setting) then you very likely will not miss this planet mesh.
Apparently this was a checkbox option in X Plane 10, but for whatever reason was removed from the UI in X Plane 11.
Any changes you make to your X Plane installation is your own responsibility.