Thank you, your technical knowledge is very helpful for understanding how things works in renderers but unfortunately this not help for creating the same image look that offer another renderer because developers using the same technical data implemented them little different.
After another day of investigation and testing, finally I found what is going on !
I know now, why people interested in creating good looking exterior images choose Corona or Vray. Not because Octane is worse. Because these renderers oriented for exteriors have great built-in calibrated settings where you can create simple materials, using built-in light system, pressing render and excellent, great pleasure for eye image is done. In Octane to achieve the same you must tweaking. People are lazy in nature.
From left to right - Octane, Corona. This time without cheating with gamma or ambient occlusion. The same camera exposure.
HDR Lighting :
Hosek & Wilkie lighting :
You can get color picker, I prefer MS PowerToys which has on-screen HSV picker
https://github.com/microsoft/PowerToys/ ... ag/v0.76.2 and you can see that every the same part of images have the same color, saturation and brightness level with error max 5%.
They looks EXACTLY the same. So where is problem ? Why 80% of the architectural visualization market use Corona, VRay not Octane ? Because Octane has badly implemented material brightness calibration and bad default values for SkyLight !
1. Main problem in Octane are materials. They are strange compared to Corona because Octane color brightness on 80% are the same that Corona use on 50%. When you want more photons to be pushed out and lighting darker areas you must use 15-35% more material brightness for that here. The same situation is for color saturation. Octane needs 5-15% more saturated color for create the same color expansion from one material to another. Especially visible in interiors.
Material brightness in Corona from 50% to 100% are the same in Octane using 85-100% values. Something wrong is with calibration here. We have much more possibility to set slider within material darkness than in its brightness.
2. Octane Hosek @ Wilkie looks little different in Corona. The most important thing is that Octane Sun Power is way too strong by default. It create too dark shadow areas in relation to Sky power. To make it the same as in Corona it should be set to 0.4 if Sky Power is set to 1. After that we have more brightness in shadow areas with not too much dark shadow.
This solution works fine for simple colored materials but not for textured ones. Every color texture needs to have much more power to achieve the same bright expansion in GI by using additional color correction node or by power in image node - still needs to tweak.
I will share these scenes for both Octane and Corona so you can play with it within day or two.
