ogre is rendering engine and if you can had the time to work with the sdk it would be a good choice. It's free and powerfull.

you also also unity but it's only working mac for the developpers

S2 is also an alternative.

if you can afford it Unigine is a great tool, stunning graphics and features.

truevison is good but not much better than a7.

but for me Ogre remain the best choice. It's free powerfull with a huge list of contributors and developpers, and good features