View distance of 3D in Google Earth

When you place a 3D model in Google Google Earth you can use KML to decide how close the viewer has to be in order for it to be visible. For technical details on how this works and how to implement it see the KML documentation. This effect doesn’t just apply to 3D models but works for other KML features, such as placemarks and polygons. Google Earth Pro uses this concept for the regionation tool we looked at last month.

Today we are looking at how a similar effect is used by Google Earth to display its 3D imagery. As you fly around in Google Earth, you will notice that the 3D imagery fades out in the distance. However, if you actually measure the distance that it fades out, it varies considerably from location to location. It also varies depending on what screen size you are viewing Google Earth at. At full screen we found that for parts of New York, the limit is about 8km, whereas in Tokyo it is up to 30km.

Clearly, Google sets the maximum view distance for each piece of 3D imagery and they are not consistent. In fact, in New York there is a curious effect where you can sometimes see more distant imagery but not the imagery in the mid-field.

Presumably the reason for implementing the maximum view distance is to avoid possible issues with too much 3D being displayed at once. However, we believe that the maximum distance displayed could safely be increased quite a lot and we hope Google will consider increasing it.

New York

In the above view of New York the old type of 3D buildings (1) from the Sketchup 3D warehouse can be seen at great distances, far exceeding that of the automatically generated 3D. The bridge in the distance (2) and the neighbouring buildings become visible before some of the nearer 3D imagery (3) next to Central Park.

About Timothy Whitehead

Timothy has been using Google Earth since 2004 when it was still called Keyhole before it was renamed Google Earth in 2005 and has been a huge fan ever since. He is a programmer working for Red Wing Aerobatx and lives in Cape Town, South Africa.






PLEASE NOTE: Google Earth Blog is no longer writing regular posts. As a result, we are not accepting new comments or questions about Google Earth. If you have a question, use the official Google Earth and Maps Forums or the Google Earth Community Forums.

Comments

  1. The Bridge at (2) is a far more prominent feature so it makes sense to have it be visible at a greater distance than some random city blocks. The Buildings at (1) were made with sketchup and are extremely low poly so they don’t take much to display at a greater distance.

    However when looking at the scenery in your picture with GE myself I noticed that at the same position and perspective I could see all the new 3D just fine, city blocks going all the way to the bridge at (2).
    And I could only find one possible explanation: resolution
    The larger your GE window the further it shows 3D Buildings.
    I tested it with a vm (2560×1920) with ge maximized and different smaller window sizes from about the same perspective as in your picture (maybe a bit further south).

    At around 800×600 GE would barely render the buildings around the south of central park
    At around 1280×800 It looks similar to your pic, the sketchup buildings(1) show up, blocks near (3) are missing.
    At 1920×1080 GE renders everything in 3D far beyond the bridge at (2), which is about 12 km from my pov. So the draw Distance should be about 20 km as it stops short of yonkers.
    At 2560×1784 GE starts to render the Tappan Zee Bridge which is almost 30 (!!!)km from my pov.
    I took some screenshots and put them on flickr to illustrate it:
    https://flic.kr/s/aHsk8yw59C

  2. This short viewing distance of the 3D cities irks me somewhat because I often like to position the camera somewhere near the ground or adjacent to a tall building/landform to see what the view of the city would be like in the distance. When distant buildings don’t render it doesn’t fairly represent the view. For example, when positioned on top of a tall building in downtown Newark 8 miles east of New York, I ought to be able to see the Manhattan skyline in the distance. However I cannot. Or when positioned next to the Hollywood sign I cannot see the downtown LA skyline.

    Also, I have noticed that the view distance varies among cities and even within cities themselves. Chicago, Denver, Nashville, Mexico City, and Kansas City have exceptionally long viewing distances. Oddly though in the case of Chicago, half of downtown disappears when the camera goes too far away.

  3. When i last worked with KML and GE, there was a thing called Level of Detail, i think, whereby we can specify a minimum count of display pixels required, for any given geographic feature, before it gets displayed, as we zoom in. The number of displayed pixels is of course a function of the size of the feature, the distance from viewpoint, and the scale of the current map/earth. I may not have explained it well but it made perfect sense to me and it worked. How does it all relate to what you now describe? Did they change how they do things?

  4. my take: The loading/unloading of 3d imagery it not just based direct distance from viewer.

    Location (2) is on a slight hill slanted towards the user camera compared to (3), and is therefore more visible in the scene.

    This is a fast rule to use when making decision whether to load or unload terrain geometry. It’s more sensible than just using simple distance, but it’s not perfect.

    In an app like Google Earth, an improvement would be to also use the average height (or maximum height) of geometry in that blocks that are being loaded/unloaded. So, if the block of geom has skyscrapers it should load earlier and hangaround longer.

    You can see this effect better in a place like San Francisco. If you fly in over the Bay up Market St heading towards Twin Peaks. The 3D imagery on the hill loads before the valleys in front of it.

    Andrew | eResearch | University of Western Sydney

  5. I really hope they give you the ability to change the FOV and 3D view distance in future updates

  6. You can set Google Earth’s field of view either in KML or with “ViewSync/horizFov=DEGREES” setting in the client’s “drivers.ini” config file.



PLEASE NOTE: Google Earth Blog is no longer writing regular posts. As a result, we are not accepting new comments or questions about Google Earth. If you have a question, use the official Google Earth and Maps Forums or the Google Earth Community Forums.