Hey everyone. I just made a rather detailed post about how to get the most out of TG3 quality settings and I thought it might make a good sticky post for all to read.
First and of greatest importance do *not* assume that the max on all sliders is the best, or is appropriate for all renders. This is particularly true for the Global Illumination sliders. Most people who use GI in practice use values between 2 and 4. For basic scenes 2 is fine in fact.
Now on to the rest of the info about quality settings.
For general detail setup, to know what to change when trying to improve image quality, follow these rules:
Do a test render with general default quality first.
Remember that there are multiple places where detail settings are changed.
Also keep in mind that there are lots more detail settings than before and they affect different aspects of the scene. Never assume that you just need to turn everything up or on for best results. Some settings are only necessary for certain scene types and will just slow down other renders.
If you see noise in your clouds, increase cloud Quality. If you see noise in the atmosphere, either below or above the clouds, or in light rays, increase atmosphere samples.
For atmosphere samples, the default of 16 is good for many situations, especially in normal daylight without "god rays", etc. To reduce noise you may need to increase beyond 16, but I wouldn't go above 64 unless you have lots of rays, in which case you might go as high as 128. Don't go above that though as you get diminishing returns for very much longer render times.
Cloud Quality is usually best left at 1, going above 1 will increase render time considerably, but may be necessary with certain extreme settings and when not using Raytraced Atmosphere. Note the 3 main factors that influence render time are: The *taller* your clouds (higher "depth"), the more *dense* they are, and the more *edge sharpness* they have, the more samples will be needed for good quality, and since samples are adjusted automatically based on Quality, if you leave Quality at 1 but increase any of those 3 cloud settings, your render time will go up while the system tries to maintain quality by increasing samples.
For atmosphere the quality is defined by number of samples and is indicated by the level of noise. For clouds the quality is determined by the Quality value in the cloud layer, which corresponds to an internal number of samples that varies based on other settings in your cloud layer. If you don't see noise in your clouds or atmosphere but want higher "quality" (e.g. edge fidelity, detail), don't increase samples, just increase Detail in the Renderer.
Once you get a good level of noise-free results with clouds and atmosphere at 0.5 detail you can adjust other settings.
If your lighting seems to need more detail or accuracy you can try increasing GI detail. I would try 1 level at a time, go from 2 to 3, then 3 to 4 if it's not enough. If you don't see noticeable differences in these changes then your problem probably lies elsewhere!
If you see jagged edges on areas of high contrast (terrain against the sky for example) or object edges, increase Antialiasing. Note that in the free Technology Preview you can't go above 4. For Terragen 3 licensed versions you can use whatever value you want, but I would not recommend going above 8 or at most 12 in general, and 4-6 should be fine in most cases. Scenes with large amounts of fine vegetation may need more, but values above 16 should never be used unless you really know what you're doing.
Finally, once you have a pretty good-looking scene and all your other detail levels have been adjusted appropriately, if you still feel that the *overall* scene lacks a bit of detail, then you can consider increasing the main Detail setting. But again I would recommend adjusting other detail first until you have a fairly consistent level of quality across the whole render. Even if it's less *ovearll* quality than you want, the main thing is that it be consistent - noise-free clouds, decent surface detail, good lighting quality, etc.
Increase the main Detail setting incrementally - don't just jump to the maximum. Each 0.1 increase will have a big impact on render time as well as quality, but the render time impact is generally greater than the quality impact. 0.5 actually provides pretty good detail for many scenes. 0.7 or 0.8 can be a good detail setting for final renders while still saving time over 1.0. You might even use 0.9 for almost the same detail as 1.0 and less render time.
Don't simply assume that you will always be able to see the difference because 1.0 has more detail than 0.9. TG2 renders *sub-pixel* detail, so it is not necessarily the case that you would see the difference between two high quality render settings (0.9 and 1.0 for example).
That's it for now. I hope that will help give you a better idea of how to get reasonable render times *and* quality.