Daz 3D’s Iray Render Settings Deep Dive – Part 1

Now that you’ve thrown together a few renders in Daz 3D, and you’re thinking about figuring out more, you might be wondering what all the options in the render settings tab mean and where you could tweak them for more efficient rendering. Well wonder no more! Armed with Nvidia’s Iray Programmer’s Guide, I’m going to have a look through every setting and see what I can find!

The General tab is mostly self explanatory. You can choose your Dimension Preset, or set your Pixel Size or Aspect Ratio yourself. The aspect ratio will recalculate according to the pixel size you set, and if Constrain Proportions is on, then the Width or Height pixel number will change to fit the aspect ratio.

Render Type lets you choose between Still Image, Image Series, and Movie. The Render Target is only available in still image mode, and has two options: Direct To File, and New Window. Direct to file will render directly to a file on your system, while new window will bring up a window while rendering that will let you change certain settings on the fly. We’ll take a closer look at those settings at a later date. Rendering to a new window will cause a slight performance hit, and while it can be useful in proofing a render as it happens, for the most part it’s better to go direct to file.

Image Name is the filename to save to, and Image Path lets you choose a different location to the render library. The Auto Headlamp setting will enable or disable the automatic headlamp on Daz 3D’s cameras depending on this setting. Never, of course, leaves them off, but the other option, When No Scene Lights, will turn on the auto headlamp on your cameras if there are no Daz 3D lights in the scene. This can be problematic if you’ve lit your scene with HDRIs or emissive surfaces only, as the headlamp will come on and mess up your lighting.

When switching to image series or movie modes, the Render Range option becomes available. This lets you tell Daz 3D which frames of your animation timeline you want to render. This is useful when you want the first few frames from one camera, and then some on another camera, and so on. The Series Base is where you set the filename for your image series. Whatever you set will have a three digit frame number appended to it for the filename.

Rendering movies directly from Daz 3D has never worked for me, but when selected, the only filetype that can be chosen is AVI. I personally prefer the flexibility of rendering frames then using After Effects to create the movie, but everyone has their own preference.

Finally, and for more advanced users, is the Post Process Script option. That’s not going to be part of this guide, but it lets you run a script after the render is finished.

Now, we’re going to skip the Render Mode in this part and go straight to the Progressive Rendering settings. These settings assume that the render mode is set to Photoreal.

The first two settings aren’t talked about much, but the Min Update Samples is the minimum amount of samples the renderer will process per loop. The Update Interval is how long the renderer will loop for before writing an update to the target (file or window). Longer times lead to more efficient rendering because of fewer interruptions to the renderer for updates.

Min and Max Samples are the minimum and maximum iterations the renderer will go through, and the Max Time is the maximum amount of time the renderer will render for.

Rendering Quality is a way for Iray to determine if any further iterations are necessary. Enabling it will enable the Rendering Quality and Rendering Converged Ratio options. Increasing the rendering quality will increase the rendering time, but it will also reduce noise, while the converged ratio will determine whether a render has ended based on how effective further iterations are. If more iterations won’t make a visible difference based on the percentage converged, then the render will end.

Rendering quality can be left at 1 if you’re using either the built-in post denoiser, or another denoiser. Any benefit to the image from setting it higher will be gained from denoisers.

Iray will stop rendering a scene if either the max samples, max time, or converged ratio is reached. Increasing the converged ratio beyond 99% will usually get Iray to spin its wheels until either the max time or the max samples is reached. It’s arguable that with the post denoiser, a converged ratio of 95% will achieve the same or better results than a 99% ratio and a render quality of 2. It’s also worth mentioning here that you could render at 4k resolution up to 50% with the denoiser, then downsample to 1080p in Photoshop to get great image quality, but that doesn’t help when you’re trying to put together a high resolution image.

The Optimization section has some fun stuff in it. The Max Path Length will limit the number of bounces lights are allowed to make before they’re ignored. A setting of 8 in a hall of mirrors will stop the reflections at a certain point. Setting it to -1 will let light bounce around until it loses its luminance. Reducing the path length is useful for emission object heavy scenes, especially ones with some reflections, but other lights out of viewport that won’t affect the lit objects.

To give you an example of how the setting makes a difference, I rendered a quick Hall of Mirrors scene.

The image on the left has the max path length set to 8, and as you can see, the mirror reflections stop suddenly. The image on the right has it set to -1, and the reflections gradually fade to black.

The Caustic Sampler can help reduce rendering times when you have caustic objects in your scene. Caustics are things that light passes through, like liquids, frosted glass, etc. If you’re rendering a pool scene where you can see through the water, the caustic sampler will reduce your overall render time, even though each iteration will take a little longer. If there are only a few caustic objects in your scene, the caustic sampler may actually make the render take longer. This is a scene dependant option that can be experimented with per scene.

The Instancing Optimization only makes a difference if you’re using instances in your scene. If you are, then optimizing for speed may cause you to hit memory issues, while optimizing for memory may slow down your render. The setting won’t effect scenes without instances.

Ray Tracing Low Memory is only used in pre-Turing cards, so non RTX cards. It’s also used in CPU rendering. It will help to reduce your GPU’s memory utilisation, but if you’re on a newer GPU, this can be set to Auto and ignored.

Now, to the final section for this part, Filtering.

The Firefly Filter Enable option enables the firefly filter to reduce fireflies, small dots that stay bright as the render progresses. It’s best to leave it on, however its efficacy depends on the Nominal Luminance setting. If the nominal luminance is set to 0, then the firefly filter will try to base it’s calculations on the Tone Mapping settings, but that may not work as well as setting a nominal luminance. The number you set it to will vary based on your scene. For a darker, night-time scene, you might want it to be low, but for a brighter daytime scene, increasing it would be better. It’s a good idea to experiment with the setting, and see what works. Of course, the post denoiser will remove many of the fireflies in your scene anyway, so the benefit may be largely moot.

Noise Degrain Filtering will bring up a few noise reduction options, but for the most part, using the Post Denoiser is much more effective.

The Bloom Filter Enable option turns on the bloom filter and lets you add some nice bloom to the emissive lights in your scene. This works beautifully with the depth of field options in the Daz 3D camera. You can adjust the Bloom Filter Threshold to only apply the filter to brighter lights in the scene, and the Bloom Filter Brightness Scale will increase the brightness of the bloom effect.

Pixel Filters are advanced mathematic functions that help you sharpen or blur your render. A too sharp render can highlight details, while a little blur can make it more realistic. If you’re usually adding some Gaussian blur while post processing in Photoshop, you can skip that step and do it in the render. The choice of pixel filter algorithm used is entirely up to you. I personally prefer the Mitchell filter, but it’s just aesthetics.

The post denoiser enables Nvidia’s Deep Learning based denoiser. You have to have both Post Denoiser Available and Post Denoiser Enable set to on for it to work. The Post Denoiser Start Iteration is where the denoiser will kick in, and start denoising. The main reason for keeping this reasonably high is when you’re using Iray mode in the viewport. The denoiser can make moving around the viewport in Iray mode slower.

I’ll end this part of the deep dive on the Post Denoise Alpha setting; leave it off, because it’ll slow things down. Denoising the alpha channel effectively doubles the denoising time, so unless you’re getting a lot of noise in your alpha channels, best to ignore it. In the current release version of Daz 3D (4.15.0.2), the newer SSIM (Structural Similarity Index Measure) denoiser options are there, but hidden. I’ll write up an article about those later in the series.

Next time I’ll look at Spectral Rendering, Section Caps, and more.

Did you pick up something new with this deep dive? Did I miss something? Let me know in the comments!