3D Sky Creation - Frank Kane Describes His Experience In Teamwork With Vizerra

  Early in Vizerra’s development, 3DreamTeam recognized the need to have skies to match the photorealism of the virtual landmarks they were creating. They partnered with Sundog Software, makers of the SilverLining™ sky, cloud, and weather rendering engine, to create virtual skies to match Vizerra’s scenes. SilverLining had met the needs of many games and visual simulation applications in the past, but Vizerra demanded a whole new level of realism. Over a period of several months, 3DreamTeam and Sundog Software worked closely to refine SilverLining and its integration into Vizerra. The end result was both Vizerra and SilverLining becoming much better products as a result of this very fruitful collaboration.

Sundog Software is based in Seattle, Washington, USA - completely on the other side of the planet from 3DreamTeam. But, this worked to our advantage - while the folks at Sundog were sleeping, the 3DreamTeam was busy trying out their latest adjustments and features to the skies, and providing a constant stream of feedback for Sundog to address the next morning. We captured some interesting “before” and “after” screenshots along the way to illustrate the progress we made together.

One of the first things we worked on was the look of sunrises and sunsets. Originally, the skies looked too yellow at these times of day (the area marked “1“) and the lighting on the clouds wasn‘t as dramatic as it should have been (“2“):

Sundog tracked this down to an error in how the effects of ozone on sunlight were being simulated; after applying this fix and increasing the resolution at which lighting on the clouds was computed, you can see that we ended up with much nicer effects at dawn, with a nice orange glow at the horizon blending up toward a deep blue sky toward the zenith:

Another issue we worked on was the look of the sky at twilight. This was a particularly difficult time of day to simulate using the physical techniques SilverLining used. When we started collaborating, twilight skies were very flat, much too bright, and even purple colored:

3DreamTeam pointed this out, and sent along this reference photo for Sundog to use while perfecting the look at this time of day:

Sundog Software went back and refined how it applied “perceptual tone-mapping” during this time of day;
essentially, an effect intended to simulate the loss of color perception at night had gone a little haywire, and
actual experimental data from an old Naval almanac from the 1960’s was used to simulate what happens to
the sky just after the sun falls below the horizon. After applying these improvements, truly dramatic
twilight scenes in Vizerra became possible, as below:

Another issue we addressed was that SilverLining’s clouds originally looked rather flat-shaded under
certain conditions, such as when they were being lit head-on from a sun directly opposite them:

By introducing support for “high-dynamic range” rendering (“HDR”) in SilverLining, we gave
3DreamTeam the ability to have much finer control over how SilverLining’s lighting results on the clouds
would be displayed. We also added some extra random noise to the individual puffs that make up the
clouds, giving them more depth. The results were dramatic:

Together, this cross-continental partnership between 3DreamTeam and Sundog Software helped make both
of our products exceptionally better. The two companies continue to provide feedback to each other and
help each other out, most recently in testing out and refining a cloud and sky plug-in for the game design
tools that 3DreamTeam uses. We’ve really enjoyed working with each other - both teams have worked
hard, but the end results are truly exciting!

Frank Kane, Sundog Software LLC