Here’s a post I’ve been meaning to write up for a while now but seeing as it’s critical to the next lesson I’m creating I can’t ignore it anymore.
For those that know me, you’ll know I love the realism Octane gives out of the box but the user demand for V-Ray is obviously a lot higher due to it being a much better overall tenderer for production.
However, there is one thing sorely lacking in V-Rray and that is realtime Film Response curves.
Octane has an awesome tone mapper inside which allows you to apply different real world film responses to the image while being able to adjust gamma (To compensate for some of the curves baking in different gammas)
For me personally, I love working with Octane but in all honesty, 90% of that reason is because it gives more realistic renders out of the box not because it’s easier to work with (Even though the rendering speed also plays a large part)
so for the sake of my subscribers who aren’t prepared to swap I’ve made it my mission to figure out why exactly Octane renders look better.
So far I’ve encountered a few reasons for that.
-(Be default it uses it’s own implementation of the GGX BRDF, that doesn’t produce the weird “spreading” on the grazing angles that V-Rays does.
-Gi simply looks different, it feels more real in shadow areas and with bounced light.
-Octane has 40 or so film response curves and realtime tone mapping that can drastically alter the look of a render with little effort and all the realistic work I’ve done in Octane uses them.
So this thread is partly a request for these curves to be implemented but also I’ve got a couple of questions to ask.
The only way I currently know how to implement the film response curves is through the Motiva ExposureControl plugin for V-Ray http://www.motivacg.com/en/exposurecontrol/ which has all the same curves as Octane.
Below you’ll see a render comparing Octane to V-Ray.
If the gamma is set to 1 in the tonemapper we get a very dark and dirty looking image so in the Octane tonemapper you correct this to be 2.2 (Or whatever you want really for artistic reasons) and all of the reflections/highlights aren’t compressed. so you can raise the gamma and basically the detail is still in the image.
Now below that there is the V-Ray version using the Motiva exposurecontrol plugin (which provides these film responses)
Loading in the same response curve gives a similar result (I’m still not happy) but we now have the problem of the gamma being too dark. So the only way I know how to adjust that in V-Ray is to change the images curve in the frame buffer. (For some reason V-Rays gamma correction in the color options doesn’t work with this plugin)
Doing this though creates really rough banding and the detail simply isn’t visible in the dark areas.
Maybe if you check this out Vlado or one of the devs you could shed some light on the differences between the two. I’d love nothing more than to be able to show subscribers how to match the look of Octane.
Octane does some really weird stuff (subtle reflections are visible in the GI pass etc) and it’s very difficult to get V-Ray to behave the same.
Cheers for any help, it’s 6am and I’ve been experimenting 16 hours straight so apologies if this is a weirdly written thread.
Below is a screenshot showing some of the curves octane uses
