Here's the comparison between Corona, V-Ray, Redshift, Octane, and Arnold Render. Tried my best to get the identical result & minimize the difference between the renderer engines. The hardware specs: i7 4790k with GTX 780.
Corona
V-Ray
Redshift
Octane Render
MAXtoA (Arnold Render)
From the result render of this emissive material scene, here's what I've got:a. Corona build 2017-11-10The indirect lighting from Corona is the best of all in the terms of the best quality of image output from GI WITH less noise level OR less render time.
b. V-Ray adv 3.60.03Definitely slower than Corona for the same quality output image. Btw, I don't wanna use it anymore, but I still need some essential feature from it and because of more freedom in the settings.
c. Redshift 2.5.40Redshift actually can be the fastest than others in the term of less noise level OR less render time "
IF" I change the GI & tweak some settings, but it sacrifice the quality of the image output from GI. Since the indirect lighting is the big problem for render time in Redshift, the only solution is to use the mesh light to clear up the noise faster.
d. Octane Render 3.06.4 - 4.41It's pretty fast, but still can't beat corona in this scene.
Btw, out of this topic, if you read some advantage and disadvantage of this GPU renderer:
https://www.ronenbekerman.com/unbaised-gpu-rendering-what-is-the-big-deal/And this for another:
https://www.ronenbekerman.com/unbiased-gpu-rendering-octanerender-vs-fstormrender/In my opinion, I don't see any bright future in the near future for this renderer, cause of the major development is realy slow and maybe because of it's dark history...
e. MAXtoA 1.1.880 (Arnold Render)The render time is the slowest in this scene compared to the other 4 render engines. Arnold Render is really slow when handling indirect lighting from the diffuse ray like Redshift. The solution is to use the mesh light like redshift too. Btw, monte carlo have some trouble to denoise the render sample for now. So, maybe Arnold Render can't have denoise feature in the near future.
*Here's my request list to make Corona be a better render engine:A. Near future version:1. Please fix this:
Corona can't handle indirect lighting from PhoenixFD fire properly. The result is the overwhelming noise in the indirect diffuse pass stays like forever. The example scene (fireplace) attached below. Cache the simulation first using PhoenixFD, then go to frame 300 and render it.
2. Shadow/Light mode of Falloff map.
Corona doesn't support it.
3. Mesh Light.
Other renderer engine could be much faster using this light for that scene. I believe corona can be more faster too with this.
4. Bucket render.
Bucket render seems can handle more sample in the same time than progressive render. The result is less noise OR less render time.
5. Roughness settings in CoronaMtl.
Many render engine have it, like V-Ray, Redshift, Octane, Arnold Render.
B. Future version:Corona RT or fully support GPU engine like Redshift or Octane, but must be with out of core GPU memory like Redshift. Is there any chance to recruit the ex-developer from Octane or Redshift ;)
Personally, Corona is and still the best renderer engine for me. I'm sorry if I'm wrong, cos I'm still very young and not the expert in rendering.