You spent hours creating the best scene you’ve ever created, you press F12 to see the rendered result. The final result is a grainy render that doesn’t look good at all. So how can we remove the grain from a render in Blender?
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The quick and simple solution
The solution in 99% of the cases is very simple. You just raise the number of samples used in Cycles. This can be done in the Render Properties when you have Cycles enabled. A lower sample count means more grain, noise, and “fireflies” (those white pixels that show up sometimes). Just bear in mind that having a higher sample count will also increase the render time. If you find that rendering times are slow, check out our guide on how to speed up cycles.
Oh and with the latest release of Blender we have a pretty nice denoising feature, this is enabled in the same panel as the sample count. If you’re lucky you might not even need to raise the samples, denoising could solve all your grainy issues with your renders.
Why is this happening?
Cycles simulates light from emitter sources and predicts how it will bounce off objects and materials in an environment via path tracing. However, not all light sources are treated equally, and Cycles cannot always predict every light ray or its route, resulting in noise and grain. Having more samples will help Cycles calculate the paths better, giving us less noise and grain.
Removing fireflies in a render
And let us talk about fireflies, those white burnt-out pixels you can sometimes get when you render a glossy or transparent material. These can sometimes really be a pain in the butt to get rid of without any denoising, I’ve had some scenes where I increased the sample count by a lot and still got them! You might think a simple denoise pass will help, and yes, sometimes that will work. But denoising problematic areas can also create weird artifacts or distort the actual render. So it’s better to go to the root of the cause and see if we can fix it there first.
Multiple Importance Sampling
Multiple Importance Sampling is something that is enabled by default in Blender. It helps Cycles to calculate the paths better, resulting in a much cleaner render but not necessarily 100% noise and grain-free. The reason why is because it treats all the elements in a scene differently, so while the fireflies of a certain object in the scene can disappear, other objects in the scene can still have fireflies. You might’ve figured it out already, but Multiple Importance Sampling of course comes at the cost of increasing your render times.