Another commercial software. I also tried Reality4D and 3dRAD. However, the trial limitations of Walkabout3D will not cripple my purpose. But, is still trial, I think I could also give a go with Crytek and Oblivion game engines or maybe IrrEdit. Guys, do you know other free or open-source softwares that do this stuff?

Welcome Geocine! Nice looking avatar . I didn't sign any 'NDA' so luckily I can mock the slow dev as much as I want, without spilling any of that top secret Pentagon mumbo jumbo. But seriously: we all are impatient to see what the next SU will be like.