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.

Following, I will list a set of common issues I encountered, and then discuss useful tips and tricks that I found within Daz Studio, to solve them.

Tips and Tricks for Daz Studio Beginners. Image rendered in Daz Studio 4.6 Pro with postwork in Photoshop.

1. Dealing with Poke Through in Clothing

One common problem in 3D-posing software is that depending on pose, the body of our figure may sometimes poke through her clothing. In addition, when a figure is wearing multiple layers of clothing, an inner shirt may poke through an outer vest or belt. Similar poke through issues can also occur with hair and head-wear.

In the past, we deal with this issue by manually adjusting or enlarging various parts of our wardrobe. Another technique is to make a body part that is fully covered, invisible. For example, if our figure’s toe is poking through her boots, we may turn off the visibility of her entire foot.

In Daz Studio, we can address this thorny issue by using their collision detection function.

To get to this function, we access our clothing parameters.

For example, in the screen-shot below, we have added some hair and clothing to our Olympia 6 figure. Next, we select our clothing top (JG_Top), and then click on the Parameters tab, which is right below the Scene tab.

Added hair and clothing to my Olympia 6 figure.

Accessing the collision detection feature for a piece of clothing.

On the Parameters screen, we want to select Mesh Smoothing, which is where the collision detection feature resides.

Note that Enable Smoothing must be on for collision detection to work. We can then set the collision item and the number of collision iterations.

In the case of clothing, our collision item is usually our figure. However, if we are wearing multiple layers of clothing, we can also set the collision item to be another piece of clothing. For example, we may set the collision item of a belt to the pants, instead of to our base figure.

The default collision iterations of 3 usually works for most things, but if there is still poke through, we can try raising this figure to resolve it.

How to add the Mesh Smoothing functionality.

Most new clothing items already come with the Mesh Smoothing feature included. However, for older pieces of clothing, it may not be present. In this case, we can add the Mesh Smoothing function from within Daz Studio.

To do this,

1. Go back to the Scene tab.
2. Select the object that we want to add mesh smoothing to.
3. Click the the button with a triangle and some lines on the top left of the Scene panel (highlighted to the right).

This will open up a drop-down menu. We want to mouse over the Edit option, which will open up even more object feature options. To apply mesh smoothing and collision detection to an object, we simply select Apply Smoothing Modifier from the top of the drop down menu.

Note however, that adding this mesh function will require additional calculations, which may slow down navigation and increase render time. Therefore, we only want to only include it as necessary.

In the case of mesh smoothing, additional calculations need to be made when our figure pose is changed, which can significantly slow down direct manipulation posing controls. If I have clothing items with high smoothing or collision iterations, I usually turn mesh smoothing off while testing and tweaking poses. There are also vendor products that can help with poke-through such as Zev0’s Fit Control

Make sure there is no poke through between the figure and her clothing by using the collision detection feature.

2. Getting Rid of Blocky or Jagged Figures and Objects

Sometimes, an object in our scene may appear blocky or jagged when viewed up close. This is because there are not enough polygons on the surface of the object (i.e. not enough resolution). Therefore, when we zoom in, we start to see the jagged corners of the now larger polygons that make up the surface.

This is similar to when we zoom into an image, and start seeing jagged edges, because each pixel is now much larger and we start seeing the jagged corners of the pixels.

How to add sub-division surfaces to a figure or object.

Another very useful Daz Studio mesh function is the Convert to SubD option. SubD stands for subdivision surfaces. Using this option, we can automatically add more polygons onto our object surfaces. By increasing the resolution of our objects, we get rid of jagged edges and increase the quality of our renders.

We can increase the object resolution by using the same process as outlined above for mesh smoothing.

1. Go back to the Scene tab.
2. Select the object that we want to add mesh smoothing to.
3. Click the the button with a triangle and some lines on the top left of the Scene panel (highlighted to the right).
4. Then, we select Edit > Geometry > Convert to SubD.

For example, in the dark angel picture below, I used the sub-division surface feature to increase the resolution of the wonderful End of Summer Hair on my figure. In addition, I also used the Mesh Smoothing operation we discussed in the previous section, to further smoothen out my hair edges.

I applied mesh smoothing as well as sub-division surfaces to the hair object on this dark angel. It helped to significantly smoothen out the jaggies in his long hair.

We can access our sub division surface parameters by selecting the object, clicking on the Parameters tab, and then choosing Mesh Resolution.

Mesh Resolution or sub-division surface parameters.

Wheel icon to the right of the sub-division level panel.

Note – if we want to increase our sub-division level by more than 2, we only need to click on the wheel icon at the right of the sub-division level panel (shown to the right).

This opens up a drop-down menu, and we want to select the Parameter Settings option. Doing so will open up a pop-up window that allows us to increase the maximum sub-division level in our interface (shown below).

How to increase the maximum sub-division level in our interface.

a) Remove Grid Lines on Sky-Domes

Sub-division surfaces are also really useful for removing lines in sky-domes. When certain environments are rendered, grid lines may sometimes appear on the sky-dome. When this happens, I simply select the sky-dome in my scene and convert it to a sub-division surface. Increasing its polygon resolution seems to get rid of all the grid lines.

b) Background Figures

Just as we can increase the resolution of foreground objects and figures in our scene, we can also use the sub-d controls to lower the resolution of background objects to increase rendering speed.

This is especially useful when we have multiple human figures far off in our background. These human figures have a lot of detail and are usually set to high resolution by default, which will unnecessarily slow down our rendering speed. I also make sure to reduce the mesh resolution of far away clothing and hair.

I lowered the mesh resolution of the human figures, hair, and clothing that appear on the background of the scene.

To get the blurring effect in the background,
1. Select your camera and go to the Parameters tab.
2. Select Camera from our list of parameters.
3. Turn on Depth of Field.

How to get blurring effect in the background.

Here are some simple instructions from Flipmode on how to easily set our focal distance.

Here is a more detailed tutorial from Daz on Depth of Field.

3. Change Background Color

Finally, it took me the longest time to find the controls for changing the background color of my Daz Studio scene. Changing background color is very useful for a variety of purposes including –

• We may want our scene background color to match our floor color or texture. For example, in pin-up scenes, we may set a white floor so that shadows will create a nice effect. In such a situation, setting our scene background to white also, will cause the floor to naturally merge into it.
• We may need greater contrast between the figures or other elements in our scene with respect to the scene background.
• For placing lights, it is absolutely invaluable to change our scene view to Wireframe so that there is no occlusion of our light objects. To better view a wireframe scene, we will need to change our scene background color to black or some other darker color.

Top view of wireframe scene, with a black background, which is very convenient for light placement.

How the change the background color of our Daz Studio scene.

To change our scene background color, we want to-
1. Click on the triangle with lines menu button to the right of the camera drop-down menu on the top-right of our scene. We circled this button in red in the image above.

2. This opens up a drop-down menu, and one of the options is Change Background Color.

3. Clicking on this option will open up a pop-up window with a color selector for us to pick our new background color. Once we are done, select Ok and voila, our scene background color is changed.

That’s All Folks

If you have useful Daz Studio tips and tricks, please share them with us in the comments section below. Have fun rendering with Daz Studio!

Scene created and rendered in Daz Studio 4.6 Pro. Post-work in Photoshop.