ProWalker GPU - Samples/quality settings
1. Samples: Image quality in ProWalker GPU is directly related to the number of samples calculated by Iray for each frame of an animation (or still image).
What is progressive rendering?
In progressive rendering, the entire image is calculated in increments called samples. Each new sample increases the accuracy of the image—first shapes and edges are refined, light distribution and material characteristics gradually become clearer, and finally Iray eliminates noise and artifacts until a clean render is produced.
Unlike SU Podium, an Iray render is never technically "finished." ProWalker will continue running calculations until the user tells it to stop, usually at a point of diminishing returns where additional samples do not add visibly to the quality of the image. Take a look at the images below for a demonstration of progressive rendering.
Photo-real mode - 10, 100, 500, 5000 samples:
Notice in the above example using Iray photo-real mode, 5000 samples is not sufficient to fully eliminate the noise. Required samples will vary from model to model; for this scene, at least 10,000 samples would be recommended. For an exterior scene, 5000 samples would almost always be plenty—direct sunlight is easier and faster to calculate than bounced (indirect) light in an interior.
Id mode generally requires fewer samples:
In contrast to the above example, the following images were rendered in Id mode with 450, and 1000 samples. As you can see, even at 450 samples the noise is very nearly eliminated:
The second example with 1000 samples has almost no visible artifacts, even with a relatively noisy concrete texture on the walls. Id mode is fast produces very good images, but lacks some of the nuance we can achieve in Photoreal mode at high sample levels. Nevertheless, Id mode is an extremely effective compromise for producing appealing images efficiently.
Note: ID mode uses a biased sampling algorith instead of pure pathtracing to speed up the render process. For rendering animation, ID mode is more efficient than PR mode without a drastic quality hit, however it is also somewhat prone to a noticeable "flicker" effect. A potential solution for this would be GI caching, however this has not been implemented.
Photo-real mode has advantages for still visualization:
Given time to calculate enough samples, Podium Walker's PR mode will yield the best image Iray is capable of; the most noticeable differences at high sample counts are superior reflection quality and more nuanced light/tonal distribution. Pr mode is also the only render mode that currently supports SU Podium light emitting (LEM) materials, which can be extremely useful when lighting a scene.
In the following example with 10,000 samples, noise has been reduced almost to the point of invisibility:
2. Render settings Gear icon
Podium Walker gives you three ways to set the number of samples that will be calculated for each image or frame of an animation. Quality settings are accessed via the gear icon.
- Time: Sets a maximum time limit per frame. Podium Walker calculates additional samples until the time limit is reached, and either saves a still image or moves onto the next frame.
- Samples: Specifies a precise number of samples per frame. Use this if you've already done test renders and know how many samples are required for your desired image quality.
- Automatic: An automatic solution that attempts to find an efficient balance between speed and quality. Moving the slider toward "fine" yields higher quality imagery (more samples) but slower render times.
Setting the number of seconds per frame is the simplest way to limit the amount of time ProWalker spends rendering an animation—simply multiply seconds by the number of frames in your animation and you can estimate the total render time. Then adjust this value to fit your time budget.
However, before rendering a full animation, it is essential that you make test frames to determine a sample count that produces an acceptible image quality for your project. With a limited time-budget, there is usually going to be some compromise between higher quality images and number of frames (length of animation)—it's up to you to determine where that balance lies.