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For example, when doing test renders we may reduce Rendering Quality and then push it up again for our final image. I.e., it is a quick way to increase or reduce the time at which rendering stops. In more practical terms, Sickleyield defines this parameter as a multiplier for Max Samples and Max Time. Of course speed of convergence also depends on our hardware and scene. a higher quality value will take longer to reach a given level of convergence.

Rendering Quality – Based on Tobor’s experience, this controls when the Iray renderer considers a pixel to be converged.

If we have a slower graphics card, we may want to increase Max Time. Note that the render will stop when either Max Samples or Max Time is reached.

Max Time – Controls the maximum amount of time before rendering stops.

The more samples we collect, the better our guess will be.

Max Samples – Controls the number of samples collected per-pixel.

Many of these parameters control when rendering stops, and may override each other. My Render Settings > Progressive Rendering settings. By understanding the source of noise in our Daz Studio Iray renders, we can better control it in our images. Specular and reflective surfaces increase the number of small and bright areas, each of which serves as an indirect light source. Specular, reflective, or refractive surfaces can further increase scene noise. Small bright areas with high values create more noise than wide bright areas. 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. This creates interesting light patterns on the water floor. Water, for example, bends light (refraction) and focuses it, essentially making the lighted areas smaller and brighter. This is because we are sampling for the entire volume as opposed to just the object surfaces.Īnother noise problem area is when there are caustics. If we render the point light in a volumetric space, there is also more noise. Notice that there is quite a lot of noise when a small bright light is producing most of the illumination in the scene.

Depending on the strength of the light, this value may be very high, thereby significantly skewing our average guess.īelow, we have a zoomed in image with just the point light turned on (all other lights are off). In other cases, we may randomly sample in the direction of the light, creating a higher value than reality. In some cases, our collected samples may miss the small light altogether, creating a dark spot. When it is the main source of light in a scene, there will likely be a lot of noise. 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).įor a more simple case of noise and small, very bright areas, I placed a point light between a fantasy woman’s hands. 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. For example, when most of the scene light is coming from small and bright light sources, specular indirect lighting, or doorways and windows. What Determines the Amount of Noise in an Iray Scene?īased on my own Daz Studio experiences, Iray scene noise seems most pronounced when there are small, extremely bright areas in the scene. What then determines the amount of noise in an Iray scene? As you may have noticed though, some scenes take longer to converge than others, and some scenes are more noisy than others. Noise arises when we guess incorrectly, so the value of a particular point widely differs from what it should be. As we collect more and more samples, we will ultimately converge on a likely answer. The more samples we collect or iterations we run, the more time it takes, but the better our guess will be.

Therefore, our Iray renderer must guess what the value of a point is by sampling light from a set of different but finite angles. 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. For each point on the screen, it shoots out a ray from the camera to that point, then tries to determine its color/value.

Physically based renderers, such as Iray, tries to approximate the physics of reality. It may receive light from outside, there may be shadows cast from nearby objects, and there may be indirect lighting from nearby surfaces. Any single point can receive light from an infinite number of directions. We do not normally think about it, but real-world lighting is very complex.