Not sure if this been mentioned or asked before but here goes.
Will Terragen 2 will have the ability of using a Global Radiosity as an environmental light node?
With this renderer, we'll be able to do renders more realistically like those seen in Vue 8 renders like here: http://www.cornucopia3d.com/galleries/displayimage.php?album=lastupby&cat=0&pos=14&pid=32102
So are we able to see a global radiosity node?
More info here on radiosity - http://en.wikipedia.org/wiki/Radiosity_%283D_computer_graphics%29
Here you go: http://forums.planetside.co.uk/index.php?topic=5345.msg55472#msg55472 (http://forums.planetside.co.uk/index.php?topic=5345.msg55472#msg55472)
For that image you linked however if you wanted that sort of effect you could just double your layer in photoshop, set the new layer to softlight and then add a blur to that layer. Would give you exactly what is going on in the grotto image.