Allow me to preface this post by clarifying that I have zero experience in coding, let alone complex path tracing render engines, and I certainly don’t know how Cycles works, so I do apologize if the idea you’re about to read is extremely stupid. Now, to my main point:
As a user whose graphics card is not yet supported in Cycles (I use a 2011 iMac with an AMD card), I often try to think of ways to reduce the noise in my image without having to render for hours. I’ve tried noise reduction in After Effects, but it never produces a good result, as that method involves a selective blurring of non-detailed areas. Ever since I learned about the Seed setting in the sampling menu, I’ve wondered why, if a noise pattern can be generated, can’t it also be used to smooth out a grainy image.
I had an idea that goes something like this. By rendering two images at the same number of samples but different seeds, overlaying the images and averaging their color values, you could potentially achieve a much less noisy image with faster render times. I decided to test it out and see if it could potentially work. I rendered a simple scene at 25 samples. I then changed the seed and rendered again. I brought both images into the compositor and combined them with a mix node at 50%. I also rendered a control image to compare with the composite. Here are my results:
As you can see, the combined render time of the first two images (13.62 seconds) is still slightly faster than the image with twice as many samples, and I’m not sure about this, but I think it looks slightly clearer.
Let’s say you were rendering an animation with 250 frames. Using this method (assuming it were automated), you would only save one minute, but if there were a better way mathematically to average the pixel values, you might be able to get an even better image. I tried extracting a noise map using a color difference transfer mode, but wasn’t able to implement it in any useful way. Again, I know nothing about coding or rendering, but I just thought it was an interesting idea and I wanted to share it! Let me know what you think! I apologize for the rather incoherent and nonsensical post: it’s 2:49 in the morning and I have nothing else to do!