OTOY Forums

I have been reading up on a comparison thread on the Luxology Forums.

Here: http://forums.luxology.com/topic.aspx?f ... 218&page=0

It compares Maxwell Vs Octane Vs Modo. In a few of the images the OP ended up with artifacts in his scenes that would never go away, even after 64000 samples. In order to see whether or not it was a result of the OP's lack of experience with Octane, an issue with octane or just a problem with an older version of octane, I downloaded the files and rendered them for myself. I have a GTX 580 3GB video card and am running windows 7.


The below issue was easy to fix. All that was required was setting the caustic blur to .4 (or something close to it) and the artifacts go away completely. It was clear in both Pathtrace and PMC after only 3000 samples. The below picture is the original image posted on the Luxology forums, not my own. Here you can see what I mean by "Artifacts".





This however.... I could not correct.






I rendered in both Pathtrace and PMC and fiddled with the caustic blur as well as specular settings. Alternatively these artifacts do not show up when the specular material is replaced with a glossy material with a mirror reflective surface. Only the specular causes this problem.


I did not let it render for 64,000 passes I'll admit, but I rendered it high enough to my satisfaction without seeing a reduction in the artifacts. In fact, rendering it more seemed to cause more speckling.




So:

1. Am I missing something? Are there settings that I do not know about that will fix this?
2. Or, can Octane actually not render specular glass under a sun lite sky?



Either way, it seems to be only a minor issue to me being that these artifacts can be resolved in most other scenarios. I would like to know however whether or not this is truly the case. Anyway, if you want to test it for yourself various files are available for download in that thread.


Please post here if you can fix it...


The Sunlite file can be downloaded from this page of the thread: http://forums.luxology.com/topic.aspx?f ... 218&page=2

Ok well...



It seems to be related to the sun size. You have to set the Caustics blur to a higher level, and then set the size of the sun all the way up to near max. This untouched render was set to a sun size of 19 and it is rendered in pathtracing.



I guess I fixed it..


The solution just suddenly occurred to me. Perhaps this thread will benefit someone else when they encounter problems like these.

Before adjusting sun size (as it majorly affects the lighting in your scene), try adjusting the hotpixel_removal setting. A value of 0.7 is a great starting value because it retains sharpness and also gets rid of many fireflies. See if you can bring the sun size back down and the caustic blur back to reasonable levels as to not affect your scene too much.