Grainy Render

[BennyLyon]

Hi guys,

When I stick a lid on my model and add an area light to illuminate my render is coming out very grainy on live and real time render. I've had to put the main area light up to 400watts to get the interior looking bright enough but the grain is bugging me. Any ideas would be welcome. See images below:

[andy.engelkemier]

There are a few things you can do to help it, but interiors are always going to take extra time to clear up noise.

First, your light sources will need to be as Large as possible. So if the lights in the ceilings are actually tubes, then just make them planes.
Second, light doesn't travel through clear objects very well in Keyshot. But light coming in from outside could lead to considerable contributions to the scene. So just hide the windows. You can render those later just for their reflections if you want. This way you can let in some light from outside.

And a trick I've used from other software is to render darker, but lighten the scene in post. The render shouldn't be overbright Anywhere. You can get that by just increasing brightness and contrast in photoshop or aftereffects (if you're doing animation).

Also keep your lights down as low as possible. That kind of goes along with the last comment there. The brighter a light is (per volume of light), the more likely it will create noise. 1x1x1 light at 1000 will create a decent amount of light, but the scene is noisy. A 10x10x10 light at a value of 10 will create a decent amount of light, but you probably won't get any visible noise.

[edwardo]

Ooh, floating train seats!

Good tips Andy!

[fario]

interressant!

merci Andy!

[andy.engelkemier]

Oh! I almost forgot. You're reflecting things at zero glossiness. So any noise over on one side is reflected, but there's some loss there as well. That takes some extra time. I'm guessing those surfaces wouldn't be all that shiny? As they are more matte the dots are reflected, and Technically it takes longer to clear up. But in the real-time renders it actually clears up faster to an acceptable amount. This is because for every pixel that would be reflecting a mirror-like reflection, it reflects an average of pixels it sees within a certain radius of where it should be looking. That means the noise is basically blurred together. And since the pixel next to it sees a similar average, those two pixels next to eachother will have a closer result, which reduces the noise.

Try rendering it out, but reduce the sharp reflections by 10% or more if you can. When rendering with brute force unbiased style rendering I usually use at least a 2% blur on even the higher reflective objects. Unless you're looking at a Really high quality glass, everything waves just a tiny bit. Look carefully at a glossy carpaint. From far away it looks great, but when you really focus on it, it's not perfectly smooth. You'll see a small amount of wave in a crisp reflection as you slowly roll the reflection over it. You won't notice a 2% gloss, but the calculations will make it easier.