Corona Diffuse Material Reflection

[Nejc Kilar]

Hello peeps,

I've got a quick question, not sure if this was discussed before but I'm wondering whether Corona does any sort of rough (non glossy) reflections even when you only have a diffuse channel active.

I'm attaching two screen grabs of a color checker card (Thanks Dubcat :) ). These are by no means scientific and the tonemapping is different in the both of them but it does illustrate what I mean very well.

One color checker card is noticeably brighter, it has this nice rough reflection like property to it. Thats a render from Corona. The other renderer on the other hand, it doesn't have that effect.

So, I guess I'm just wondering, is there perhaps an extra reflection like property that the current Corona material is doing even if reflections are disabled? Maybe its a property of the diffuse model?

Curious to hear your thoughts!

[TomG]

Nope, no extra reflection going on. As a note, in the real world, there isn't actually a difference between rough reflection and diffuse, it's all the same light being bounced from a surface (diffuse is just reflections that are scattered in all directions, the ultimate in rough reflections) - that said, it doesn't mean that Corona with just diffuse exhibits a greater "reflection like" look than other render engines (assuming those render engines are coded correctly).

So differences here most likely are the tonemapping, and as to the correctness of the unknown renderer, we can't say. Corona looks correct for what a diffuse only surface should look like under these conditions. And possibly GI, depending on how the other engine is handling it (if it is).

[maru]

It looks almost as if the color checker was loaded with different gamma. The rest of the image stays almost the same. The difference in overall brightness/contrast/saturation of the checker differs a lot.

[Nejc Kilar]

Right, so thank you both for chiming in here :) The other renderer is a fellow pathtracer and to your point Maru, its Dubcat's awesome Photographic lut for Corona there which slightly amplify the effect and it definitely makes the color behave more as I would typically except if I'd compare it to a camera.

Still, I suppose I was wondering if maybe Corona is using a lambertian / oren nayar / whatever model that does some glossiness effects under such conditions.