Unrealistic Earth -Moon simulation

Hi

I worked on a VR app of our Solar system recently and stumbled onto something rather unusual. Using relative 3D model sizes of moon and earth distances I fail to get a realistic view of the moon. It looks way too tiny compared to how we see it from Earth orbit let alone from ground level. Ive found that I need like 1/3 of the reported 385 000 km Earth moon distance to generate Earth rise or Moon rise images that resemble those from actual NASA footage.

Am I missing something in camera settings to correct for this defect?

 

Do you have correct FoV settings?
Do you use Doubles, to accurate position / scale celestial bodies. Alternatively, did you position and scaled them correctly?

 

I worked with these numbers. Earth diameter 12760 km. Moon diameter 3476 km. Distance between centres 385000 km. So in Unity for a fixed Earth scale the moon model is placed 30 earth diameters away and is 1/3.67 th the size of the Earth model. My camera is set at 60 degrees fov.

If my camera is near the Earth say close to orbit what must be the scale size of Earth and the Field of View of the camera?

In real life if one is say in orbit at the location of the ISS thats around 400 km altitude the apparent size of the Earth disc to an observer is around 140 degrees. I need to achieve the same effect with a Mixed Reality VR headset.

 

Did you try adjust camera FoV accordingly, when at position of ISS?

 

If I adjust the fov for the camera in Unity it doesnt affect the camera at all in the Mixed Reality headset. This is what ive discovered. If I position my camera in Unity at 0.89 x the size of my Earth 3D model the view just fills up the headset boundary completely. The calculated angular size of the Earth at this distance should theoretically be 59 degrees. But the headset is claimed at 110 degrees fov. So 110 degrees in the headset is equivalent to 59 degrees angular size of the Earth model. With this relationship to get 1.9 degree angular size of the earth as viewed from the centre of the moon the moon will have to be 27.64 earth diameters away which will effectively bring it a bit closer to the earth model. This should correct for the anomaly.

 

Well didn't expected that.

But in such case, I think your best bet, is use typical game making tricks.
Either use secondary camera, which renders at "correct" distance/scale.
Or move celestial bodies closer/further.
Or scale celestial bodies, accordingly with distance.

 

The FoV shouldn't actually have any effect when it's a VR product. The actual FoV of the device should override that.

There is a nice page on Wikipedia about the Moon illusion. There are various reasons why the moon appears larger when closer to the horizon. No real formulas or anything, but at least some source for cosmetically adjusting the visual size of the moon depending on the angle with the horizon.