Well, the area light doesn't shine behind it. Actually from regular geometry objects the Omni light source is the best for matte shadow tuning. And you can exclude such a light source from shining to the other objects by setting zero for the multipliers of Reflection, Diffuse, Transmission and other layers. Only make Shadow Weight non zero

Thanks for files and advices! I have detected the issue. It has 2 issues to consider:

1) The car windows are made of glass material and this glass geometry is too close to the surrounding non-glass parts. There is some small gap between rays launching from the windows objects and the gap is too small between objects. The geometry seems to be animated a little bit for a fraction of milimeter and it's also lowpoly. So we see the windows objects slight poping that affects the interior and creates the effect of flickering.
So the first solution would be to increase the distance between windows and other car parts.

2) The second solution would be for me to fine tune the computation of this small gap that's used for rays launching from the surface.

Actually by default the material list in R25 isn't visible (I mean all that material balls at the bottom). But the selection may be active if the material it's just created and you edit it.
As for IPR it doesn't select/deselect anything, only change the statusbar when geometry updates are ongoing.
My version is R25.010. Will update to R25.25 to see what's there.

I am testing the issue right now with a scene composed of single cylinder, centileo node material + noise + gradient or anything else. In R25 with CentiLeo IPR active.
I add or remove any node alone e.g. a noise or gradient. And the rest material node system remains there. Ctrl+Z/Y works fine.
In fact CentiLeo IPR is not related to the node system in either way, they don't depend on each other.

Can you check if your material is selected in the Cinema viewport? It may happen that your entire material is selected in the list of materials and once you click "delete" this selection is removed as well together with selected gradient node. It can really be a forgotten selected material in the list, just deselect it.
What's your Cinema version?

Yes, you can combine the bump map branch and normal map using Math.Add node or any other texture.
In fact everything connected to Bump slot of material is considered as black and white bump map.
To use normal map encoding of centileo bitmap (such as blue for unchanged normal and red/green gradients for normal vector changes) you have to check "Is Normal Map" flag in centileo bitmap. Then internally the normal map will be converted to black/white image ready to connect to the Bump map slot. And you will be able to combine it with other bump maps, adding, mixing, multiplying, etc.
Also keep in mind that converted bump maps (from normal maps) may have negative values in shader network internal opeations, because they show relative change of normal vector. These negative values are relative to unchanged normal and resolve for material correctly. But you have to consider this fact when for example you Color Correct them and probably want to apply some clamp for bumps.

Send me a scene to info@centileo.com pls? I will check what's wrong there

thrimanakatha, thanks for giving the list of extra potential reasons of that flickers. Indeed the noise removers / denoisers can produce the issues on low sample counts

It's very lowpoly. Can you add a Subdivision Surface Object on top of lowpoly objects and apply 1-2 steps of subdivs?

It's certainly hard to notice any flicker based on still images. I think the a noisy and lowres video can help.
Actually there should be no any flickering because CentiLeo is unbiased. The reflecion may produce bright effects from the sun.
Also the surface of the car needs some more subdivs to get smoother however this is probably not the source of flickers.

You are right, the Sky+Environment tag supports only spherical lattitude/longitude HDRI mapping, it doesn't support mapping to camera space like tha Background object. That would be easy to modify.
At the moment background mapping can be implemented using a workaround e.g. using a plane object with material with you background and this plane object is placed in front of camera and reacts to camera movements. I think it's possible to do this with scripts but some extra skills would needed. Anyway I have to do it in a simpler way

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ssjenforcer wrote: Also, were you able to reproduce the shadow catcher bug with Area and spot lights? I assume there is still work to be done with light settings?

I have replied in that topic. Not a bug, but a specific detail of light shape. Actually I need to make light includes/excludes from illuminating the objects.

Actually this is the right finding that shadow catcher weights only for Omni, Infine lights sources and Sky+EnvMap tag.
The others lights like Area and Spot don't support casting to the shadow catcher because they have limited directional lighting, e.g. they don't lit the scene behind them. This would create unneceassary shortcomins.
On the other hand the Omni light is good, you can place it somewhere and tune the radius to get the neceassary postion and shadow softness.
Also why your shadow catcher object plane is so small? Usually it should be larger.

Hi ssjenforcer, sorry for some long reply.
Actually I see you want to fine tune the defaul light intensity multiplier when creating the light object. Also the undo/redo not working for light sources. I will check how to fix that.

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ssjenforcer wrote: 'set as default' does not apply the default setting to the centileo light object

Yes, this button works for the settings of the Cinema light source object only without considering the tags.

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ssjenforcer wrote: Also, are there plans to make the C4D background and sky objects work, so that textures can be easily mapped for backgrounds?

Do you want to apply materials to Sky object in way this is done in C4D? Currently it only works using CentiLeo environment tag - in the past I thought it was more convenient. Although there is still no Background object support. I think there will be some reconsiderations. Thanks for suggestion!

These are correct settings. I still get same results using color editing on my side. May you attach a scene file that reproduce the issue?

Did you change teh color space in project settings to something not default?
Please, can you send me the file? I can't reproduce for my case.

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Leo Allan wrote: Make sure to have youe CentiLeo Light source have the centileo light source tag. Furthermore, you can edit the overall multiplier and the gamma settings to change the level of light.

Exactly, however these tags are added automatically if the light source is created using CentiLeo menu available at the top line of C4D menu.

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ssjenforcer wrote: Ok. I actually always had Send Raw AOVs checked after you told me before that helps to match the IPR and render gamma, I believe.

The "Send Raw AOVs" option is needed only when you need to output the raw (gamma=1) HDR image without any tonemapping (or postprocessing).
By default this option is off and the tonemapping is applied, but again the tonemapping can be enabled/disabled in post processing with Enable checkbox.
Usually this Raw output is needed when you later modify the image in After Effects or whatever.

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ssjenforcer wrote: What about Shadow pass? Is that possible to have separately as well like other beauty passes? I am trying to use the alpha channel but it doesn't allow me to control the shadow. The diffuse layer also has the shadow from my shadow catcher plane, and I can't find a way to control its intensity using the extractor effect. Because the diffuse also has the shadow there is always a shadow connected to my diffuse that I cannot control the intensity.

Ok, we need to develop the decomposition of the current passes into more building blocks.

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ssjenforcer wrote: The diffuse layer also has the shadow from my shadow catcher plane, and I can't find a way to control its intensity using the extractor effect.

At the moment you can change the weight of the shadow catcher intensity (vs shadows coming from the other light sources) using the "Matte shadow Weight" option in CentiLeo light tag for Omni/Directional light sources. There is also the similar option inside CentiLeo Environment tag

As far as I remember CentiLeo follows the native camera settings quite well and DOF should be ok. Motion blur should be tested but I hope it will merge nicely for such combinations. Anyway this adds extra render time. So need to enhance to more features

Oh no, I have to make volumetrics asap to avoid all these double render tricks

This glass around a light source use some quick skip of rays through the pure glass. The recolor may help, but changing transmission roughness to quite large values may change the noise amount in some gradual way. But it works with the least noise amount on low roughness values.

Maybe using X-Particles for the droplets? They have quite more physical effects there. We support them using all the particle physical attributes