Why do the ceiling tiles in this room reflect the color of the floor?

(LBJ) #1

Why do the ceiling tiles in this room reflect the color of the ground?

I applied a brand new material to the tiles with all of the default values and it still reflects the color of the offset brick texture on the ground.

There is no glossy shader, and for some reason, the emission and specular options that are normally under the materials tab have both disappeared, in both blender render and cycles render.


#2

Diffusion transfers color too. That’s how real life works.
If you’d add more white light sources perhaps that transferred color won’t be this much visible.

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(CarlG) #3

Where is the light coming from? If window/opening near the camera, it looks like it’s reaching too far into the room. What’s the lighting, AO, and material settings?

But yeah, diffuse is the major contribution of bounced light. Glossy can only contribute light bouncing if reflection caustics is enabled. If you need to control diffuse color bleed (sometimes it can appear too strong, although it tends to be our own fault), use a mix shader with original shading into top slot, and another diffuse into the second slot with a desaturated version of the main color. Fac should be driven with lightpath/isDiffuse.

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(BeerBaron) #4

This effect is commonly called color bleeding and indeed it is something that happens in real life:

However, a lot of archviz people are complaining about not getting “white walls” because of it. It is possible to inhibit this effect with Light Path masks. Simply mix a white diffuse material (second input) with your target material (first input) and use “Is Diffuse Ray” from “Light Path” as “Factor”.

(CarlG) #5

It happens a little less in real life than in our typical Cycles setups, because we sometimes cheat and only let diffuse bounce light (reflection caustics turned off). In real life specular bounces does not pick up the color of the material (usually) just like the reflections we see from specular reflections on dielectrics are white. If we compensate for this by making the albedo brighter (or add more light), the bounced diffuse (picking up color in the process) will become more saturated. This would be more pronounced in highly glossy surfaces, probably not at all for the scene in this case which appears to be mostly diffuse.

(LBJ) #6

Here’s the file if you can figure out what’s wrong with it.

I used blender 2.79 because I’m most familiar with it’s UI.

https://1drv.ms/u/s!Ansq7V5Mt2BrghBORhhbItO--xX4

The ceiling tiles are supposed to be gray, like in a typical office.

Haven’t added a speckled texture to it yet, most PBR’s I’ve found cost money to buy.

(CarlG) #7

I have a few hours left on a render, but I’ll try it out tomorrow. Meanwhile, change the beige color tint on the floor tiles to pink and see if that shows in the ceiling. Also, If using principled, try setting specular to 0.

#8

You haven’t packed textures, so I’ve replaced concrete and wood by a simple color.
You have connected lamp material to both surface and volume as emission, don’t need to do that.
Also, try to use principled, not diffuse. Fresnel reflections are important.

I don’t see a big problem here. This would change a bit for sure if your tiles and ceiling were not ideally flat, you know - stucco, marble, wood, anything really. It changes how light is reflected.

Also, take note on the fact that your ceiling is not lit by anything but bounces.


The light it’s getting comes from bounces, and there’s not really much white stuff to bounce off from :smiley:

This is quite silly. I do like to experiment too, but don’t leave such monstriosities in your scenes like this, because they are affecting it, especially render times with that SubSurface! :smiley:
Now look what happens to ceiling when I turn it to white.

Better, right? :wink: Using textures should help a lot, even tiny white points will make a difference. Also, you can add some white stripes on the ground not visible to reflections and camera to get some white reflections.

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(CarlG) #9

Had a look at it. Most of the bounced energy is coming from the weirdly setup floor material combined with reflective caustics - a lot of glossy coming from layer weight/fresnel at blend 1, with glossy color coming from the brick texture - whuuut? The bump node in there isn’t doing anything, and a musgrave->hue that isn’t doing anything. Model is grossly out of scale making it harder to lit, with no scales applied. View transform is sRGB/Default, I prefer sRGB/Filmic. Exposure is 0, which is adequate for “office lighting”, although I’d probably turn up those lights unless a dim environment is required.

Although I agree on “everything should have fresnel”, but when the glossy roughness gets as high as this (like for fabric textures), I have no problem going full on diffuse only or diffuse+velvet.

Here is the fix style I mentioned to control color bleed - in the image I’ve plugged in an unnatural 0.25 hue full saturation node, making the bounced (now mostly diffuse) lighting pink for extreme effect in the image. Try the other input to desaturate the bounced lights.

Regarding the Material.020 node setup above, which I didn’t try. If you want to control anisotropy, use the tangent node set to UV, not the UV coordinates. Although the material resembles more of a freaky experiment :smiley:

I recommend spending time naming your objects and materials as well, possibly even organizing stuff into collections. For rooms like these (which I do a lot of), when it is mostly the room that is important and not the building and neighbouring rooms, I tend to use flat plane geometry rather than boxes for walls, ceiling, and floors, in order to utilize backface culling.