Quote from: WAS on August 23, 2019, 03:21:33 AMAnd issues like this scene I feel it's a quirk of the current state of the PT rather than it as a whole or what to expect from a finished product. Such as rogue inter-reflective scenes from one angle to another creating a 800x render difference. Definitely not normal.
The
issue you originally reported seemed to be about a 27x difference (although in that post you said "10000x"). But
you have since identified an antivirus issue that was surely affecting the result, not to mention it was also not reproducible on our systems here, nor have we had any other reports of such issues. The render time would understandably be longer at the different angle due to inter-reflection, but it was nowhere near "800x" (nor 10000x). Render times change based on many factors, including camera angle, and regardless of PT. Please stop spreading misinformation.
Furthermore, while PT is not exclusively beneficial for scenes with objects, plants, etc., it is fair to say that the results are often (but not exclusively) more
noticeable in such scenarios. This is simply because the standard renderer handles large-scale and simple light bouncing and occlusion calculations fairly well. Simple mountain, desert, rock, etc. scenes are easier for cache-based methods to do a decent job on. More complex lighting scenarios that result from multiple layers of overlapping geometry, occlusion, shadowing, etc. will
tend to show the results of path tracing more. So the advice that Ulco is giving is perhaps too strongly stated, but it is not completely wrong. Simply put, the render time difference with PT on vs. off is more likely to be worth it (i.e. to make a big difference) in more complex situations.
In the example in this scene here I'm not even sure I believe that the PT on/off comparison is quite valid because the difference is so dramatic. I wouldn't jump to conclude that the difference is due solely to PT. For example the Enviro Light has no effect with PT enabled, so if in the original the enviro light was increased (as it sounds like it might have been), then the PT version would be
inherently darker, not due to being more accurate, but simply to essentially disregarding the enviro light increase. Without knowing the rest of the scene settings it's just hard to know if it's a good comparison.
That is not to say such comparisons are not worthwhile and interesting, nor that trying PT on a scene like this is bad idea. I'm only cautioning against drawing major conclusions about PT vs. non based on comparisons like this. It will take a while before everyone fully understands the specific consequences of Terragen's path tracing mode and settings, and can thus make accurate comparisons. And we'll do our best to document and make people aware of things that might make comparison harder, like the enviro light difference.
As for the much longer render time, without knowing the full settings of the PT render I don't know if it "should" take that long or not. PT requires optimization of settings, which I've outlined elsewhere (and, yes, will be added to the docs, with even more detail). We are of course happy to work with Rich or anyone else who wants help optimizing render settings and time, that just requires sharing scene files. We'd welcome Rich getting in touch if he's interested in doing that.
- Oshyan