Hi Kaiko,
So, by opening the "
Schematic" window, you are able to see the "
Stage Schematic". If you proceed to the lower right corner there is a button "
Toggle FX/Stage Schematic". If you click it, you are then shown the powerful node-based compositing system that OT offers. You can add FX that blend vector colors. This might not give you the manual control that you are looking for, but it seems pretty great. (According to this video, which I have cued to start at the FX section:
https://youtu.be/-jjeh1USIlY?t=4m52s). I cannot yet make use of this as OT crashes in the render preview window.
Now I know, "just a Vector engine" might seem like a limitation, but believe me, it's not. Let me give you an example. Say you spend a year animating something in a raster-based animation software at 720p (This isn't horrible for YouTube or Vimeo). It is a wonderful animation, so you decide to submit it to some animation festivals. Wouldn't you hate for them to turn you down simply because it wasn't a high enough resolution. I believe most movie theaters show 2K - 4K these days. Most traditional animation was captured using film, which is still arguably higher quality that digital video today so this wasn't necessarily a problem. Raster software inherently limits the potential of your drawings by binding them to a fixed pixel/grid based system. Vector, however, stores the lines' coordinates and parameters in a mathematical fashion, as to be scaled to whatever size necessary without a loss in quality. You could argue that this puts some limitations on line variation and color blending, but I believe the preservation of your hard earned time and effort is what is most important.
This is where OpenToonz comes in. Even if you spent years working in a raster-based software and someone turns down your submission because of resolution, then OpenToonz could convert all of your lines to vector for you! You are still probably thinking, "Yeah, but what about color blending?" So, it is obvious that the FX engine has some powerful color blending techniques. I assume that it applies these FX to the vector images based on output resolution. So it would only make sense that whatever size you render out your frames as, the FX will always be applied in that quality. Therefore, you can always have premium color blending at the touch of a button. Literally. Resize, render, and now you have a newly blended set of frames.
I hope this helps clarify some of the major advantages of vector animation. Most of vector gets a bad reputation because of automatic tweening, but I believe that it has great significance in frame-by-frame animation as well.