The main common reason that a render would turn out differently than the preview is if you have moved the camera in the preview but not "Set"/Copied it to the actual current camera position. That does not appear to be the case from the TGD. I think there is something going on in what you're doing to create those cloud shapes. The Ray-Traced Preview renders in a different way than the main preview, and if you let the main preview refine to detail 20, it too goes black. The regular render process works more like the main preview than RTP, so this makes sense. The bottom line is there's something weird in your cloud setup (very extreme values coming out of that setup, I would guess). If you connect just a regular density shader to that same cloud layer it renders fine in both preview and final render. Also note that if you just connect the Perlin 3D scalar to the *input* of the Merge Shader 02, you suddenly get normal looking (and cool-shaped) clouds that render tine. Maybe that was more what you are after?
On another note, I think maybe we are seeing why you are getting such huge render times even on your new box: you have some very high and unnecessary atmosphere settings which are really making render times very, very slow. *Especially* when you're experimenting with new and unusual ways of shaping clouds, as you seem to obviously be doing here. I would first recommend to disable "Receive Shadows" from both cloud and atmosphere, as Fleetwood suggested. Neither setting in this scene will have any positive or noticeable effect, but both will make render times much higher. You may be feeling like enabling all of this now that you have a faster machine, but that is just going to take away any performance benefit you would have scene, and as I mentioned in many cases you will have no benefit for it either. Receive Shadows should be enabled cautiously in any scene, and you should really know why you are enabling it and where you expect these shadows to be cast into your clouds/atmosphere from.
The other performance issue is the high atmosphere samples. Terragen 4 has Defer Atmosphere enabled by default, which means in general you want to use *much* lower numbers of samples for your atmosphere than if you were rendering without Defer. In this case 64 atmosphere samples is just crazy. 16 should be fine, even with AA2. If you use higher AA, you should definitely not use any more than 16 atmo samples, unless you have a heavily shadowed atmosphere and there is obvious noise in its darker areas.
- Oshyan
