Skill Level Intermediate
- [Instructor] The Arnold renderer is a brute force Monte Carlo renderer and it's main limitation is that it will output a fairly grainy image unless you employ some special techniques such as adaptive sampling or as we'll see this week, post process denoising. And there are two different ways of denoising an image in Arnold. One is designed for active shade and the other is designed for production rendering. Let's take a look. Go into the render setup dialogue, and I've got that set up for active shade mode. If we go to the Arnold Renderer tab we'll see that I've got some pretty low sample settings and I've disabled adaptive sampling. And because most of the light in this scene is indirect, we're going to get a very grainy image. But, if we go over to the denoiser tab here, we have a couple options. We'll see optics denoiser and Arnold denoiser. The Arnold denoiser is disabled for active shade mode. It will only work in a production rendering but the optics denoiser from Nvidia is designed for an interactive production rendering. And when we turn apply on beauty on, then if we have an Nvidia video card, then after the active shade rendering has completed, an additional post process will run and apply a blur to the image. So let's click on render. And first we see a preview pass, and then the actual buckets of the final active shade rendering appear as squares on the image. And once the last bucket has been drawn then the optics denoiser algorithm will run. So watch closely as the last buckets draw, and boom. Now we see we've got a blurry image with no grain. So if we had better quality settings for our sampling we would have better results here but because our sample settings were so low, we're getting, really, way too much blur and in fact, the lamp in the corner here is completely disappearing. But again, if we had set our Arnold renderer sample settings higher to begin with, then the problem here would be less extreme. Right, so that is the optics denoiser. Let's now talk about the production renderer denoiser. Switch the render setup target over to production rendering. And back in the denoiser tab, we now have access to the Arnold denoiser, also known as noice, N-O-I-C-E. And the process here is, we save out a special file which is a denoising AOV and then we load that AOV back into this window and run the denoise algorithm. So it's a completely post process after the rendering has completed. We can enable output denoising AOVs but we also need to define a file output. So let's go into the common tab, and we can scroll down and click on render output files. And in the project folders, render output, I've got a couple of PNG files there just to illustrate what it would look like if you ran the optics routine on a production rendering, but we're going to use noice this time, and that requires an EXR file. So for the save as type, you want to choose OpenEXR, and it needs to be an EXR file so that the AOV that is saved out for denoising is in the correct format. And we also need to choose a file name here, I'll call it Arnold denoise. All right, and then when I click save, I should see the OpenEXR configuration dialogue. I'm just going to take the default options there. Click OK. And now we're saving out an EXR document as our main rendering, and that's also known as the beauty pass, and it will include any exposure control. Back in the denoiser tab, the AOV that we're going to output will have the same name but will have the words noice output appended to it. And in this version of 3DS Max and Arnold, we will not get any exposure control on our denoiser image. That's kind of a limitation if you're used to using exposure control. If you want to color correct or tone map your image, you'll need to do that in post if you're using the denoiser. All right, I'll click render to begin that production rendering. Once that's completed, we can see the beauty pass with exposure control applied. Let's also take a look at the denoise AOV. File menu and choose view image file. Here's our beauty pass which is already loaded into the render view. Let's load up Arnold denoise noice input and click open. And just click OK in the OpenEXR configuration dialogue. Here is the rendering without any exposure control. And it's got some special data stored in the EXR file to allow the denoiser to run more intelligently. So let's run that algorithm. We'll go back over to render setup. And we have an input and an output. Click to browse for the input file and that will be Arnold denoise noice input. Click open. And we also need to define an output. So click on browse once again, and we'll just change the name here, we'll call it Arnold denoise noice output. And click save. There are some options down here we can play around with to control the denoising algorithm behavior. But in fact, the default settings are pretty good so I'm going to leave those alone and just click the denoise button, and we'll run the denoise algorithm just on that single frame. We get a log down here that tells us what's going on. And then once it's finished, it'll say denoising complete. Let's take a look at the output. Go back to file, view image file and choose arnold_denoise_Noice_Output.EXR and click open. Once again click OK in openEXR configuration. And here is a before and after of the denoising, and it looks pretty good. There's a little bit of noise still remaining here. We can probably eliminate some of that if we changed our sample settings or maybe changed the settings for the denoiser itself. Once again, I'll mention that this process is not compatible with exposure control and that's because AOVs ignore exposure control. If you want to use denoising, you really are forced at this point to grade your images in post in a program like Photoshop or AfterFX. One last point, we can also save our denoiser AOVs manually instead of this automatic process here. We can turn off output denoising AOVs, go to the AOVs tab and we can actually add AOV files in the built in section, and we will see that there are denoise variants of many of these AOVs. So, if we wanted to, for example, do the entire beauty pass, we can add an RGBA denoise AOV and that would accomplish the same thing as if we had enabled this switch here. But if we did it manually through the AOVs here, we would have more control, we'd be able to, for example, save out denoise AOVs for different render components. And that's how to use the optics and noice denoisers in Max 2A or Arnold.