I’ve been trying this for a few days, and I’m not getting anywhere. This is an Old’ish scene (Blender 2.76) that I eventually rendered in Lux, and I like how it turned out. However, Lux/Blender integration is still flakey, so time to use Blender 2.79, with the Principled shader to do it again.
Now, there are several things I like about the Lux render, such as the reflection and highlights, which I’m just not getting to with Cycles. Note the tiles at the back, with Lux look so much better, and even on the mugs, the fresnel seems more realistic.
All diffuse textures are perfectly colour matched. I’ve done my best with the tile bump (though I can’t match it exactly), and I’ve tried to match reflection/IOR etc as best I can.
In cycles, the colours are too saturated, the reflections are too white etc.
If anyone can tell me the math to convert between the two, I will bow down on my knees and pray to to you.
Now, I appreciate that the noise in the tiles is different. I’m not concerned about that, it’s the lighting and reflection that I’m concerned about.
I apologise for the lack of images. Dunno why that happened. They are all fully packed, but if you want to add them (not necessary for the question) they are either packed here or they are in the Cycles blend.
You are quite right. However, it’s not just the white balance that’s wrong, or the strength of the reflections, but the whole colour balance is wrong. My aim is to get the two as close to each other as possible without post work.
In the Lux render, since the environment is jpg rather than a genuine hdri, I cranked the gamma up to 4.4. In Cycles, that blows it out, and 2.2 seems a fair comparison. Even so, the Lux render has a much warmer feel. I could colour correct the environment texture, but I’d rather figure out why Lux is warmer, and why the reflections are muted in Cycles.
It might just be the way they deal with the .jpg environment map. I don’t have Lux so I can’t compare, but the overall colour seems improved by changing the right side colour ramp for the tiles to 1.00; 0976; 1.00 (increase R to 1.00)
Have you tried using the Filmic Colour Management? The tonemapping it provides simply makes the dynamic range smoother and more realistic. In any case, it looks as though the specularity of the shader in Cycles is too low. Try cranking that up to 1. I shall experiment with your scene to see what could be done to make it more like the LuxRender version.
Ok, there were several issues with the scene and I have made some corrections to make the lighting more similar to the LuxRender version.
1. Ambient Occusion
You have used ambient occlusion in your scene to approximate indirect ambient lighting. This is a big no no if you want your scenes remotely looking like a LuxRender render. I have turned this off and changed the brightness of the environment image from 5 to 12. This made the intensity of the overall lighting more similar to LuxRender and made reflections more clear and less ‘white’.
2. Colour-Ramp As you have noted, there is an issue with colour balance. The culprit behind this was the slight green tint applied to your Colour-Ramp node. I have replaced this with a neutral colour and this completely removed the cast seen earlier. This meant that the colour correction you applied was no longer necessary.
3. Filmic Tonemapping Blender 2.79 introduced a new filmic tonemapping feature that smooths out the transition to clipped areas of the scene. This massively increases the dynamic range of the final image, preventing any ‘blown-out’ areas of the scene. Colours now desaturate with increasing light intensity, emulating the behaviour of film. I changed the scene from sRGB to ‘Filmic’.
3. Materials The specularity of the mugs was too low, I increased them all to 1. The metalic aspect of the tiles was also too low, I increased this, making the material more similar to the LuxRender one. I also decreased the roughness, which was a touch too high compared to the scene in LuxRender.
There are other minor things such as samples which I have bumped to 512, which was about the minimum for this scene with the denoiser.
Thank you. My intermediate experiments did identify two of the issues that you have identified, being to turn off AO completely and to add filmic tonemapping, both of which improved the Cycles render. Having said that, I had to ramp up the brightness of the environment at the same time, and increasing the gamma at the same time (3.3) also helped.
At the same time, removing the blue tint from the tile texture helped to warm it up a little (as suggested by organic), but there’s still something missing with the Cycles render. I think a part of it may be that Lux has done something (and I don;t know what) to suggest an uneveness to the tiles to the left of the render, which adds a degree of realism. I realise that I could do this in Cycles with extra work, but not sure why Lux is doing it in the first place.
I’m going to keep going with this just as a learning and experimental project. If I can match the two closely enough, I can abandon Lux (which has some stability issues and fewer features).
EDIT: I do think that the use of a jpg as the environment rather than a true HDRI was part of the original mistake, but that’s the challenge I have set myself now.
This is where I got to in my most recent changes. Still at 300 samples with denoising rather than increasing. It’s better, but still lacks the warmth.
Probably also worth pointing out that, using default colour mapping results in the tiles along the back being far too blown out on the left hand side, whilst filmic seems to mute it a little too much.
It’s probably also worth mentioning that this is the only scene I have that I rebuilt specifically for Lux, and so other scenes built only for Cycles would probably not notice the difference.
This is where I got to in my most recent changes. Still at 300 samples with denoising rather than increasing. It’s better, but still lacks the warmth.
Probably also worth pointing out that, using default colour mapping results in the tiles along the back being far too blown out on the left hand side, whilst filmic seems to mute it a little too much.
It’s probably also worth mentioning that this is the only scene I have that I rebuilt specifically for Lux, and so other scenes built only for Cycles would probably not notice the difference.
This is a combination of your changes and mine, and whilst it still lacks the warmth of the Lux render, it’s getting there. It’s also starting to look more pleasing.
I can probably tint the environment to bring the warmth, and that may be a task for Saturday morning.
EDIT: I’ve just done a side by side comparison. I prefer this to Lux. Forget what I said about the “warmth”. They are on a par. In fact, this is probably slightly warmer. Thank you
