Reducing noise: cycles fluorescent lamps


I am currently working on a hallway scene with fluorescent lamps. The walls are diffuse shaders, and there’s no glossy or glass (at least not in this part of the scene). The armatures (something like this) are on another layer, and I’m using the compositor to add it in the scene. By setting the maximum diffuse bounces to 2, there’s less noise now, but it’s still too much. When I used half cylinders with an emission material instead of spots, it just got worse, however, the lighting pattern looked more natural.
Caustics don’t seem to make a difference, and clamp wasn’t very helpful either …

I will use it for an animation, so my goal is to keep my render time as low as possible.
Any suggestions?

Spotlights, 50 samples:

Half cylinder with emission material, 50 samples

Thanks in advance,

Add a new plane emission under the fluorescent ones and adjust the size and value. That will clean it up.
You can make the plane’s geo invisible to camera here. With the plane selected uncheck the camera box.

Have fun with it. You can add more light colors.

Thanks for the reply!
However, that’s kind of what I did with the half cylinders. It works, but there’s still more noise than with regular spots …
Any other ideas?

What cylinders?
A bright enough emit value will eat the noise away. Then you can color curve it in the compositor.

Invisible half cylinders under the lamps:

if you have a walkthrough then try baking just no object moving then

I think no matter what you do with your lighting you’re going to have trouble getting this to clear with just 50 samples.
Is there a particular reason why you’re using the Path Tracer rather than the Branched Path Tracer? I find in these situations the Branched Path Tracer is a better option as it allows you to target the samples where they’re needed.

In this case you’ll definitely need more Diffuse samples and if you’re using a Mesh Light then you’ll also need to increase the Mesh Light samples.

If you use just spotlights try increasing the number of samples for the Spotlight. How many samples are you giving the Spotlights?
The first image you posted with just the Spot lights doesn’t look too bad, some extra samples to the Spot lights might be enough to clear the remaining noise.

Instead of 3 cylinders use 1 new long plane. The cylinders are crashing with eachother giving all that noise.

It’s not the fact that there’s 3 of them (well, ok, it is, but that’s not all that’s going on). It’s that they’re cylinder meshes. The more complex (polycount-wise) a mesh light is, the more difficult it is to sample efficiently. One long plane will be efficient, but also less realistic because there shouldn’t be light coming from the space between fixtures. Multiple lamps does make more things to sample, but in this case it’s probably worth it if you can spare the render time at all. Personally, I’d use an area lamp under each fixture. (same setup as the spots, just change the lamp type to area)

Some other things:

-Area lamps use a more efficient sample scheme than mesh lights, use them instead of emitting planes. Don’t forget to enable the “multiple importance” option. This should give similar noise as the spots, but with a more realistic throw pattern.

-Cylinders are not the correct throw pattern either, there’s no possible way a light ray can come out of that fixture and end up on the path of a ray coming off the top edges or caps off those cylinders. A plane (area light) over the bottom is the closest approximation.

-Use the ray visibility switches on the object instead of using light-path in the shader to ray-switch to transparent. Ray visibility disables the intersection check entirely, rather than forcing it to complete and call the shader, only to end up with the same result as no intersection.

-Worse, that light path setup enables transparent shadows on that mat, because it has a transparent BSDF. Even though it’s not actually possible to get transparent shadows from it (this can’t be known until the shader is run). Meaning shadow rays that hit the cylinder will call the shader for no reason. Leave off the transparent BSDF and use light path!

Also you can remove the wall behind the camera. Enclosed spaces like this create noise without some intense light inside them.

You may simple need to bake the textures, and your rendering speed problem is over!!

The Branched Path Tracer helps, but not that much. With 30 AA samples (3 for diffuse and 3 for the area lights) it took over 7 minutes to render one frame at 960x540. I tried baking the textures, but it doesn’t seem to work … Could anyone briefly explain this or link a tutorial/other thread?
What I did was enter edit mode, select one of the materials, smart unwrapped, saved as a new image, then added an image texture node (not connected) and clicked bake in the render tab, with the image texture node selected.

Thanks a lot for the replies!

tttapa I will assume there is no wall behind your camera. And, at no point did you mention render times. And, for those of us using modest graphic cards for animating it’s all about render time. And, that’s the reason I can’t use Cycles, or a raytracer, for any but the simplest interior animation. But, when I saw your post I thought a chance to play in Cycles.

I’m uploading two (2) PGNs and look at the render time for Diffuse: 1 & Diffuse: 2 in the upper left hand corner. Also we don’t know what your expectations are on render times. Believe me 2:20 is a luxury I don’t often have. And, yes we stripped Cycles down to almost Direct lighting to get that but… I have a completely enclosed scene I’m doing using Yafaray, Direct Ltg.-Caustics-AOL, which I just got down to 5 to 6 minutes a frame and I’m happier then a sissy in a CC Camp. Rendering animations for many hobbyist is simply a BITCH. And, 3 minutes a frame is nothing.

Also when the camera is moving most of us accept some noise. When your camera stops as in a walk through lay on some more passes. And, noise you can call film grain. :slight_smile: Actually, many times it does resemble grain in Cycles so you are lucky there. Best of luck with your project.

Bake parts that don’t move if it’s a flythrough

Andrew price who is great on quality has a tutorial on baking textures for animation. When you bake to textures you have to up the samples. but its done once and thats it!

One method to make fluorescent lights without the massive noise (100 samples using CMJ)
Cycles_arealampExample.blend (531 KB)

There are real emissive cylinders within the casing (to increase realism), but they can’t cast light out of it and MIS on them is set to ‘off’. The real magic happens with an actual arealamp situated just below

Koumis & reC are absolutely right since you might want to bake some scenes. Hell I didn’t realize how easy it is in Cycles. One thing to keep in mind through is everything in an animation can end up as a close-up. tttapa, notice the render time below with a bake. And, you will no doubt become way more proficient then I am since you are a regular Cycles user. Once again best of luck with your animating.

Thanks a lot! Baking seems like the ideal solution.
However, I still can’t get it right, it works for the ceiling and the floor, but not for the walls. I’m guessing that the blue stripe is the culprit, every wall consists of 3 faces and 2 materials … Any suggestions for baking this? Or is baking meshes with multiple materials simply not possible?

tttapa I should be the last man to answer this. Since I had used baking only several times years ago and that was in BI. But, in post #17 I did have a different material on the ceiling and it did seem to be a problem. So I took the half ass way out (Artistic License) and made the materials on the walls all the same. And, I unwrapped the walls with mark seams but used ‘Smart Unwrap’ or whatever it is with the other objects.

Also the size of the texture. Tutorials suggest 1024 I believe. But, that didn’t work even in this simple hallway for me. Maybe the lighting contrast but I had to use 2048. It seems to me I remember faces, materials, being joined for baking albeit separate bakes are better resolution wise. You could try that. Joining the material I mean. But, it sounds like you are well on the way. For all I know a hallway like this could take several bakes to be done right.

Here’s a thought. Make each wall only one face and make the stripe a separate colored plane snapped to the wall. So it’s not even selected when you bake. Yeah, that might work. And, could look much nicer.

Try multibake addon for cycles, google it.