Discussion of image quality when developing scenery textures

[RealScenery]

Many of the RealScenery forum discussions have discussed image quality. Below is a brief, but pretty complete, overview of why you sometimes see a lot of quality differences in imagery in online mapping sites and the challenges when working with imagery covering a large area.

As envious as I am of the fine aircraft developers here, creating scenery is a whole different animal. I can't start with a blank canvas in a 3D program or Photoshop and start painting a picture of the landscape. I have to start with something (imagery) and then see how to best enhance it for X-Plane.

There are two types of imagery:

1. Aerial photography

2. Satellite imagery

Like most things, there are advantages/disadvantages to each. Aerial photography is flown with specially outfitted aircraft that have that as their sole mission in life; to take pictures. My flight instructor flew a King Air for a state transportation department that was designed for taking aerial photos. Here in the USA, much of this imagery is available at low cost, however, the tradeoff is that the imagery is much more difficult to obtain over a large area that offers consistent quality.

Satellite imagery has the benefit of having tonal consistency over a broader area, but is very expensive to license. The cost of NorCal licensed from one of these vendors would be well over $100,000USD. However, even an area as large as NorCal would essentially be a "patchwork" of imagery, even from a satellite vendor.

There are many factors that affect the quality of the aerial photography. Imagine an airplane flying back and forth across an area (called "flightlines") capturing images. As the day goes on...

...the sun angle changes.

...clouds can appear causing shadows (or sometimes even appear in the imagery!)

...middle and high level clouds can cause widespread changes in image quality compared to direct sunlight.

...changes in humidity/smoke can add to more/less scattering of blue light in the atmosphere, causing coloration changes, sometimes significant.

Seasonal differences and rainfall also contribute to vegetation differences in imagery, both aerial and satellite, if an image's neighboring images are taken months apart.

Now imagine covering an area as large as northern California (this package really covers 2/3 of the state). You can't possibly fly this area in one day capturing all of the imagery. Even if you had several aircraft, you would have different weather conditions over the area which would make the imagery from one aircraft not necessarily match seamlessly with the imagery from another aircraft, especially if the flightlines were flown several hours apart in time.

Even satellite imagery from the major online mapping sites covering NorCal is a total patchwork of images. Not all areas are being continuously captured. Most imagery is captured based on a specific order from a government agency or private company. This is especially true for aerial photography. Since much of this imagery is only acquired "on demand," imagine creating a seamless set of imagery for an area as large as a state! As you can imagine, it is very difficult to do.

The bottom line is that imagery covering a large area, whether satellite or aerial photography, is typically made up of many different image sources covering different times, sometimes even different seasons and different years! The NorCal scenery for X-Plane is no different. However, I've spent a lot of time making it as consistent as possible. What you see in the NorCal gallery is representative of the image quality throughout the entire NorCal area. I think I can say with a good degree of confidence that this is probably one of the most consistent set of images covering northern California that exists today, especially from aerial photographs.

Now that's only one factor - the source imagery. The other major factor affecting your perception of the images is your computer's video hardware including your video card and your monitor. I use two machines in my scenery production and they have different monitors and video cards, which, of course, render the images differently, as well as all of my other software.

How about X-Plane? I mentioned above the difference in sun angle and time of day. X-Plane also does this, as we all know. Hold down the "K" or "L" keys and watch what happens as the day goes by in just a few seconds. If you have clouds, notice what happens to the imagery in the shadows versus sunlight. X-Plane will render most scenery bright and washed out at high-noon. X-Plane will render scenery textures best at mid-morning and mid-afternoon.

X-Plane now has the ability to change gamma. I design scenery with the gamma setting of 2.5. A lower gamma will make the images look more saturated, but overall, the sim will be darker. You'll have to experiment with the gamma to get the best balance of image quality, and aircraft rendering quality. You may also consider adjusting your monitor for the best X-Plane experience.

Just for fun, I picked an area in Google Maps and Bing Maps and compared it to the imagery I have acquired for this RealScenery release. I think you may be surprised at what you see here. Keep in mind these are small-scale images to give you an idea of the quality differences over a larger area. The actual images used in this release are much higher resolution than you see here. Look at the gallery link posted earlier to see the actual detail you will see in X-Plane. This is for an area north of San Francisco in the Napa Valley, home to California's famous wine country.

Overall, I think you'll find this scenery is spectacular, as I've tried to show with the examples in the gallery. Like all scenery, it's much nicer "in sim" than any still screenshot can portray.

Enjoy!

Bing Maps

Google Maps

RealScenery source image

Keep in mind, this source image above is shown at a much lower resolution than was actually used in NorCal in order to show a large area. Also, this image is our starting point, not a processed, finished image.

Eric

[Jim Kallinen]

Hi Eric, you have your Bing and Google images reversed, but it makes little difference to what you saying. 

[RealScenery]

Fixed! Thank you, sir!