Physically based renderers, such as Iray, tries to approximate the physics of reality. For each point on the screen, it shoots out a ray from the camera to that point, then tries to determine its color/value. However, it is simply not possible to calculate the value of a point with real-world accuracy, because we would need to sample light coming in from an infinite number of directions.

Therefore, our Iray renderer must guess what the value of a point is by sampling light from a set of different but finite angles. The more samples we collect or iterations we run, the more time it takes, but the better our guess will be. As we collect more and more samples, we will ultimately converge on a likely answer.

Noise arises when we guess incorrectly, so the value of a particular point widely differs from what it should be. As you may have noticed though, some scenes take longer to converge than others, and some scenes are more noisy than others. What then determines the amount of noise in an Iray scene?

Why Is There Noise in My Daz Studio Iray Render and How to Remove It

What Determines the Amount of Noise in an Iray Scene?

Based on my own Daz Studio experiences, Iray scene noise seems most pronounced when there are small, extremely bright areas in the scene. For example, when most of the scene light is coming from small and bright light sources, specular indirect lighting, or doorways and windows.

In the Fantasy Girl with Horns scene above, there are many bright but small areas of light in the environment map because the sun is peeking through the trees. These small areas of light create noise on the water, which gets compounded as it bounces off that surface and hits others objects in the scene (indirect lighting).

For a more simple case of noise and small, very bright areas, I placed a point light between a fantasy woman’s hands. A point light has a small surface area. When it is the main source of light in a scene, there will likely be a lot of noise.

In some cases, our collected samples may miss the small light altogether, creating a dark spot. In other cases, we may randomly sample in the direction of the light, creating a higher value than reality. Depending on the strength of the light, this value may be very high, thereby significantly skewing our average guess.

Below, we have a zoomed in image with just the point light turned on (all other lights are off). Notice that there is quite a lot of noise when a small bright light is producing most of the illumination in the scene.

Zoomed in image with just the point light turned on. Rendered in Daz Studio Iray for about 10 minutes.

If we increase the strength of the point light, then the picture noise increases (see below).

Point light strength increased by a factor of 10. Rendered in Daz Studio Iray for about 10 minutes.

If we render the point light in a volumetric space, there is even more noise. This is because we are sampling for the entire volume (including the points in-between the hands), which increases the frequency of errors.

If we render the point light in a volumetric space, there is also more noise. This is because we are sampling for the entire volume as opposed to just the object surfaces.

Another noise problem area is when there are caustics. Water, for example, bends light (refraction) and focuses it, essentially making the lighted areas smaller and brighter. This creates interesting light patterns on the water floor. However, because of this light bending property, the direction of our pixel samples become even more important and more susceptible to light misses or accidental hits.

The general take-away here is that –

Small bright areas with high values create more noise than wide bright areas.

Specular, reflective, or refractive surfaces can further increase scene noise. Specular and reflective surfaces increase the number of small and bright areas, each of which serves as an indirect light source. By understanding the source of noise in our Daz Studio Iray renders, we can better control it in our images.

How Do We Reduce Noise in Our Iray Render?

I use four key methods to reduce noise in my Daz Studio Iray images.

1. Adjust Iray Render Settings.
2. Increase the amount of light in the scene.
3. Render at a higher resolution (larger image), then resize down to average out the noise.
4. Remove some of the noise in post-work by using despeckle or blur operations in Photoshop.

1. Adjust Iray Render Settings to Reduce Noise

One of the easiest ways to reduce noise in our Iray renders is to increase the number of samples we collect. The more samples we collect, the better our guess will be (i.e. the closer our guess converges to the actual value). We can do this by going to the Render Settings tab, and then selecting Progressive Rendering.

My Render Settings > Progressive Rendering settings.

Many of these parameters control when rendering stops, and may override each other.

• Max Samples – Controls the number of samples collected per-pixel. The more samples we collect, the better our guess will be.
• Max Time – Controls the maximum amount of time before rendering stops. Note that the render will stop when either Max Samples or Max Time is reached. If we have a slower graphics card, we may want to increase Max Time.
• Rendering Quality – Based on Tobor’s experience, this controls when the Iray renderer considers a pixel to be converged. I.e. a higher quality value will take longer to reach a given level of convergence. Of course speed of convergence also depends on our hardware and scene.

  In more practical terms, Sickleyield defines this parameter as a multiplier for Max Samples and Max Time. I.e., it is a quick way to increase or reduce the time at which rendering stops. For example, when doing test renders we may reduce Rendering Quality and then push it up again for our final image.

• Rendering Converged Ratio – As I understand it convergence is a measure of how close our pixel value guess is to its real value. As such, we will never reach 100% convergence, because that is when our guess is 100% accurate, which can only happen when we have the ability to collect an infinite number of samples. As we have seen above, this measure is also partly determined by the Rendering Quality parameter.

I usually render each of my lights separately, so I end my renders manually based on the light layer. There are three more Render Settings parameters that pertain to noise.

• Firefly Filter Enable – Go to Render Settings > Filtering and make sure that Firefly Filter Enable is on. This will get the Iray renderer to filter out some of the noise in our image.
• Caustic Sampler – Go to Render Settings > Optimization. Turn on Caustic Sample *if* we have caustics in our scene. Note that this enables some additional tests in the renderer thereby increasing sampling time, so only turn it on as necessary.
• Architectural Sampler – Go to Render Settings > Optimization. Turn on Architectural Sampler if we have an internal scene with a lot of indirect lighting and light only coming from portals such windows or doors.

This post by Dave Smith has more detail on these Render Setting parameters. Increasing the number of samples collected is probably the most accurate way to reduce noise. However, it can also take a long time to converge.

2. Increase the Amount of Light

Earlier, we saw that scenes with more noise have light primarily coming directly or indirectly from small bright areas. For example, internal scenes where light is only coming from windows or doors.

One way to reduce noise is to increase the amount of light in our scene, for example by adding large mesh lights in an indoor scene or removing unnecessary walls and ceilings. Larger light sources will reduce the amount of noise in our picture. In addition, if we are getting light from many different directions, then the probability of totally missing a light source or getting overly skewed light values will be significantly reduced.

However, a problem with this approach is that we may flood our scene with too much light, thereby losing shadows, shape definition, and scene depth. The image below is an older image of mine where I used a lot of ambient light in 3Delight.

This is an older image of mine where I used a lot of ambient light in 3Delight. Because there is too much light I lose shadows and shape definition.

3. Render at a Higher Resolution

Another simple way to reduce Iray noise is to render our images at a higher resolution (larger size). When we shrink our image down in size, some of the noise will get averaged away. This is a better method than just using blurring techniques to average away the noise because it will retain picture sharpness and detail.

For example, the top image below is rendered at 1024 by 1331 pixels, at 300 iterations, and then cropped in height. The bottom image is rendered at 3000 by 3900 pixels, at 300 iterations, and then reduced in size to 1024 by 1331 pixels (similarly cropped in height). There is a lot less noise in the bottom image without a loss of sharpness or detail.

There is a lot less noise in the higher resolution image (bottom) without a loss of sharpness or detail.

4. Remove Scene Noise in Post-work

We can also remove some of the render noise in post-work using blurring or de-speckling operations. In Photoshop, I use Filter > Noise > Despeckle for less noisy renders and Filter > Blur > Gaussian Blur for noisy renders. The left image below is the original noisy render and the right image has been blurred with Gaussian Blur radius 3 pixels.

Remove Scene Noise with Blur or Despeckle operations.

The problem with Despeckle or Gaussian Blur is that we lose a lot of detail and sharpness, especially in our primary fantasy girl figure. One way to fix this is to create another render with just the girl. By removing the water, we remove a key source of noise in our scene. With a simpler scene, we can also render more iterations for a given time. Then, we use this low-noise image to sharpen the figure in our blurred image. To do this, I select the figure-sharpen layer and set the blending mode to Overlay. Then, I do Filter > Other > High Pass with a radius of 5 pixels.

Left – Gaussian Blurred image with much less noise but loss of detail. Right – Same image but with the girl figure sharpened using the technique described above.

Conclusion

I reduce noise in my Daz Studio Iray renders by using all four of the techniques above. However, I make sure to properly balance them out so that I do not weaken scene lighting, lose scene detail, or spend too much time rendering.

There are other methods for controlling noise in a path tracer like Iray. For example, seeding the renderer differently, clamping maximum light values, and more. However, as far as I know, such render settings are not currently available in Daz Studio. In any case, they each come with their own weakness.

With just the techniques described here though, I am able to get results that I am happy with. The completed Fantasy Girl with Horns image is shown below. We have added all our lights, removed noise, and applied our post-work process.

Final Fantasy Girl with Horns image. We combined all lights, removed noise, and warmed up the image in post.

This tutorial is the first in a series designed to highlight and showcase the powerful abilities of the the Nik Collection, which is a suite of 7 plug-ins that provide an impressive array of photo editing capabilities: from color correction, retouching and creative effects to image sharpening and a wide range of special effects.

While they used to retail for $500 (and worth every penny) the good folks at Google are making it available to everyone free of charge because that’s their way.

Grab a copy here and let’s get started!

How to Transform Your 3D Art into a Charcoal Sketch

1. Using Silver Efex Pro 2 (Nik Collection)

In this installment, we will be using Silver Efex Pro 2 to turn this render of Antfarm’s Walker HD (see below) into a fine art charcoal study. For the duration of this tutorial, Silver Efex Pro 2 will be referred to as SEP2. Brace yourselves; technique is coming…

Basic Daz Studio 3Delight render without any additional lights.

I’ve taken a basic 3DL render without any additional lights, but obviously you can do this with any image (even a photograph) that has the proper value range into the SEP2 suite and run Antique Plate II (preset 36) with the default settings. Since you want it to look like a sketch, you mostly want a high contrast image without much midtones (those values will be lost).

Therefore, if your results aren’t looking like the example, just undo the SEP2 filter and adjust the levels until you get a good balance of lights and darks (in Photoshop). Then restore the filter with Ctrl+F. Rinse, wash, repeat until you get the desired results. Alternatively, you may also adjust contrast and brightness from within the SEP2 interface.

Once you are happy with the results, Right click > Flatten Image.

Image after applying Antique Plate II (preset 36) from the SEP2 suite in Nik Collection tools.

2. Warming Filter and Increasing Contrast

Once you have a solid base, the edges are already fading out just like an unfinished sketch. Notice how the clouds have become abstracted, almost like a doodle and they’re getting lost in all the background noise which is starting to look like paper grain. You could almost stop here, but why not push it a bit further?

Warming layer filter settings in Photoshop.

Create an adjustment layer/photo filter (in Photoshop) and select the Warming Filter(85). Ensure that Preserve Luminosity is ticked, then run the density up to around 88% or so.

Image result after applying the warming adjustment layer described above.

This is way too orange, but have no fear, we’re going to fix that now.

Photoshop layer stack after these operations.

• Copy the SEP2 (background layer) via Ctrl+J.
• Desaturate with Ctrl+shift+U.
• Invert with Ctrl+I.

The end result is shown below. This will be your layer mask, so hit Ctrl+A to select all and then cut it with Ctrl+X

Our image mask after desaturating and inverting our background (original) image.

• Duplicate the Silver Efex Pro 2 (background layer) twice.
• Apply a layer mask to the first one (Layer > Layer Mask > Reveal All).
• Go to the channels tab and then paste the layer mask in the alpha channel with Ctrl+V. Note that visibility of the layer must be on before pasting, then turn it off after.
• Set the layer to Multiply to punch up the shadows.

That’s nice but I want some more color in there, so

Photoshop layer stack after operations to punch up our shadows and add in more color.

• Merge the photo filter onto the other background layer copy. (Right click > Merge Down).
• Set the layer to Linear Light.
• Then Right click > Create Clipping Mask. See how rich those dark values just got?

Our Photoshop layer tab after performing the operations described here.

Still looks a little drab, so let’s duplicate the photo filter layer and reset the mode to Normal, but drop the opacity down to 40%.

Our 3D-art image after adding in a warming filter and punching up the shadows in Photoshop.

3. Add Hatching

To make it look more like a sketch, let’s introduce some hatching. Save what you have so far and then flatten everything (Right click > Flatten Image). Launch SEP2 and use Wet Rocks (preset 23) to get this grainy looking result.

Image result after applying the Wet Rocks (preset 23) from SEP2, in the Nik Collection tool.

Photoshop layer stack after adding Angled Strokes operations.

• Ctrl+L and enter 15/.75/255 to adjust the value range.
• Set the layer to Overlay at 40% opacity.
• Do Filter > Brush Strokes > Angled Strokes. I used 50/15/3 but if you’re doing your own image, just try for something like the image below.

Adjust Filter > Gallery > Angled Strokes until we get something that looks like this. Settings will be different depending on your image.

If you want to add some color, now would be a good time to try Hue/Saturation or even just Alt+Ctrl+L. You can keep messing around with it, but I’m done…

Final result of transforming our 3D-art render into a charcoal sketch using Photoshop and the Nik Collection tools.

Summary

While the Nik Collection was developed for photographers, any Photoshop user can tell you that Photoshop isn’t just for photographs and neither is the Nik Collection In fact, since 3D-art renders are really just simulated photographs, we will enjoy a much higher degree of overlap with the intended purpose than someone using the Nik Collection on colored line-art, for example.

I’ve began this series with a technique of turning a render into a charcoal sketch to underscore the concept that the Nik Collection has a much wider gamut of applications than mere photo editing, so you need not restrict yourself to using these filters only in the ways in which they were intended.

There are applications for the Nik Collection that the developers never even dreamed of!

In future installments, we will be exploring many different uses for the Nik Collection; some will cover the features much like a manual, while others will take it to a completely different level. Please look forward to it!

This article and all of the images within were created by the very talented Alex Ledante. Copyright © Alex Ledante. Check out his gallery here.

Depending on the artist, some things can be more effectively done in post, and some in Daz Studio. We get to decide, which techniques best help us transform what we see in our heads onto paper.

Step-by-Step Daz Studio Iray Post-Work Tutorial

My current Daz Studio Iray post-work process consists of 3 stages:

• Stage 1 – Combine Iray light layers and fix rendering artifacts.
• Stage 2 – Soften, sharpen, glow, color, and contrast.
• Stage 3 – HDR filter. We are currently using Color Efex Pro 4 from the Nik Collection. Available for free here.

All three stages are performed in Photoshop, but depending on the look that I am going for, I sometimes skip Stage 3. We will be using the Pearls image above in our step by step post-work tutorial. My recent images can be found here.

Stage 1 – Combine Lights and Fix Rendering Artifacts

Add in a soft background layer and our 5 Iray rendered light layers.

1. Add a soft image to provide an appropriate background. Here, we used one of the photographs from Lady Kassie’s Oriental background set.
2. We rendered 5 different light layers in Daz Studio Iray – Key, Fill, two Back Lights, and an Environment Map. For the Environment Map, we used the Tropical Ruins HDRi from sIBL Archives. We have Dome turned off, and saved the light layer as a PNG file.
3. We add in our light layers using the process described in How I Combine Iray Lights in Photoshop.
4. The added gray Photo Filter layer on top of our IBL layer is used to darken our IBL image, so that it fits our background and composition. By changing the gray color, we can lighten or darken our IBL layer.
5. If we zoom in on our current image, we will notice that there are certain rendering artifacts. In particular, the Asian woman’s hair collides with her thumb-nail. In addition, there is a missing pearl on the strand around her hand.

The Asian woman’s hair collides with her thumb-nail. In addition, there is a missing pearl on the strand around her hand.
6. We can fix this in post by using the Clone Stamp tool. In general, however, we want to minimize the number and extent of fixes we need to make, as we will get better results by dealing with it in Daz Studio.

Removed collisions and added in a pearl using the Clone Stamp tool.
7. Copy our completed Stage 1 image (shown below) by doing Shift + Ctrl + C (Edit > Copy Merged).
8. Create a new file by doing Ctrl + N, and then Ctrl + V to paste our Stage 1 image into the new file.

Completed Stage 1 image.

Stage 2 – Soften, Sharpen, Glow, Color, and Contrast

1. Right-click on our Stage 1 layer and select Merge Down.
2. Add glow to our image by using the process described here.

After running the Shiba Glow action on our Stage 1 image.

Re-tone or recolor our image by using a Gradient Map adjustment layer, set to Violet, Orange color range.
3. Turn off the Tint layer by clicking on the eye icon to the left of the layer.
4. Select the Glow3 layer. Do Layer > New Adjustment Layer > Gradient Map.
5. Select the Gradient Map layer and pick the Violet,Orange color range in the Adjustments menu (see right).
6. Set the blending mode of our Gradient Map layer to Screen and set opacity to 30%.
    
   We use the gradient map to retone/recolor our image. The Violet,Orange color range works well in in many cases, especially for realistic images. For fantasy pieces, I may use different colors in my gradient map.
7. Create a copy of all our layers by doing Shift + Ctrl + Alt + E (Stamp Visible).
8. Select our new layer, name it Soften, and set blending mode to Soft Light. Go to Filter > Blur > Gaussian Blur. Set the radius according to the amount of softening that you want.
9. Open our volumetric light file and paste it after our Soften layer.

Adding two softening operations – Gaussian Blur layer and our Volumetric light.

Select the Levels layer and set the middle value to 0.75 in the Adjustments menu.
10. Select the Soften layer and do Layer > New Adjustment Layer > Levels. This Levels layer will help to increase contrast in our image, so that it doesn’t look so flat. We set the middle value in the Levels adjustments settings to 0.75 (see right).
11. At this point, our image looks rather dark and a bit blurry. Therefore, we want to lighten our image and bring back some detail.

After our softening effects, the image looks rather dark and a bit blurry.

Right-click on the Environment Map layer and pick Duplicate Layer.
12. Open our Environment Map (Tropical Ruins) image. Right-click on the Environment Map layer and pick Duplicate Layer (see right). In the pop-up menu, under Destination > Document, select our current working image (see below).
     
    This will duplicate our Environment Map layer into our working document. We name the layer Lighten.

In Destination > Document, select our current working image file.

This is what our Photoshop layer stack looks like after adding the lighten and sharpen layers.
13. Set the blending mode of the Lighten layer to Screen. This will add the Environment Map light into our image. Adjust opacity to the level that we want. In this case I set it to 60%.
14. Duplicate our new Environment Map layer (this time into the same document, which is the default). Name this new layer Sharpen.
15. Set the blending mode of this new layer to Soft Light and opacity to 100%. Go to Filter > Other > High Pass. Set the radius to 5.0 pixels.
     
    This creates a sharpening layer from our Environment Map to bring back some of our image details. We can further increase sharpening by setting the layer blend mode to Overlay. As usual, we can use the opacity dial to make more minor adjustments.

 
After adding our lighten and and sharpen layers, our image is now brighter and has more detail.


Left – Before; Right – After adding the lighten and sharpen layers.

Add warm tint and a Vignette layer.
16. Turn the visibility of the Tint layer back on by clicking on the check-box to the left. This will give a warm tint to our image. We can control how warm our image is by changing the opacity of this layer.
17. Select the Tint layer and do Layer > New > Layer. This creates a new layer on top of our tint layer.
18. Select our new layer and name it Vignette. Ctrl-A to select the entire layer and do Edit > Fill. In the pop-up menu select Black as our fill color and make sure that opacity is set to 100%.
19. Set the blend mode of our Vignette layer to Multiply and opacity to 30%.
20. Do Layer > Layer Mask > Reveal All. Click on our mask layer to select it.

How to select the Elliptical Marquee Tool.
21. Select the Marquee tool on the left Photoshop toolbar. Right-click on it, and select Elliptical Marquee Tool (see right). Draw an elliptical marquee around the area of our image that we want to emphasize (e.g. her face and pearls). We can also do Edit > Free Transform to rotate and scale our elliptical marquee to get it to the right position, size, and orientation.

Draw an elliptical marquee in the area we want to emphasize. Edit > Free Transform to rotate, scale, and move, our selection.
22. Once we have it in the position that we want, do Edit > Fill > Black. This will create a light area around the part of the image we want to highlight.

Create a light area around the part of the image we want to highlight by using our Vignette layer.
23. Click somewhere else on the screen to deselect our marquee. Do Filter > Blur > Gaussian Blur to soften out the edges of our circle.
24. Duplicate our Vignette layer and set blend mode to Soft Light. This finishes our Stage 2 process.
25. As before, Copy our completed Stage 2 image (shown below) by doing Shift + Ctrl + C (Edit > Copy Merged).
26. Create a new file by doing Ctrl + N, and then Ctrl + V to paste our Stage 2 image into the new file.

Our image and layer stack after finishing the Stage 2 process.

Stage 3 – HDR Filter

1. Right-click on our Stage 2 layer and select Merge Down.
2. Click on Color Efex Pro 4 from the Nik Collection (Download for free here).
3. Select Detail Extractor in the Color Efex Pro 4 interface. In this case, I use the default settings (see below) and hit ok.

Use the Detail Extractor in Color Efex 4 from the Nik Collection to bring out more image details.

Our Detail Extractor layer with a mask for the areas we want to emphasize (e.g. face).
4. This adds a new Detail Extractor layer to our image file. We can then set the opacity of that layer to control the level of detail added. In this case, I set the opacity to 30%.
5. In addition, we may only want to add detail on certain parts of the image. To do this, select our Detail Extractor layer and do Layer > Layer Mask > Hide All. Then, paint in the areas where we want more detail.
6. Also note that the Detail Extractor operation will lighten our image. To re-balance the layer so that it better matches the original Stage 2 image, we add a Levels adjustment layer (Layer > New Adjustment Layer > Levels). Make sure to check Use Previous Layer to Create Clipping Mask, so that the Levels adjustment only applies to our Detail Extractor layer.

Make sure to check Use Previous Layer to Create Clipping Mask.
7. Set the middle number in the Levels adjustments menu to 0.9. This finishes our Stage 3 process.

I do not always use the HDR filter. For this composition, I actually prefer the softer image, so I posted the finished Stage 2 image in my Daz Gallery. In fact, this applies to all of the methods outlined above; we only apply them if they help to enhance our image. Experiment with opacity and adjustment settings to get the results that you want.

Hope you enjoyed this step-by-step post-work tutorial.

Asian woman holding pearls final image (with HDR filter).