Render Settings Explained - Quality vs. Render Time

This article is the right place to look for the best render settings for your V-Ray project.

Overview

Every project is different in terms of render quality requirements and deadlines. Some jobs require swift production for tighter schedules, while others are all about quality. Since the criteria for speed and quality vary, different sets of render settings are needed.

With the help of some simple render settings tweaks, the rendering process can be easily streamlined.

This article aims to answer questions such as:

• What are the best Render Settings for my project?
• What is the relation between image quality and render time?
• How to get the best image quality for limited render time?
• My final image renders too slow, how can I make the rendering faster?
• My final image is too noisy, how can I get a better image quality?
• Is there a way to improve the image quality without slowing down the rendering?
• How to improve image quality without restarting the render?

Image Quality and Render Time

Render production is affected mostly by two factors - image quality and render time.

It’s important to know that they are correlated - high image quality comes at the expense of long render times, and vice versa - speedy renderings produce low image quality.

Start with Default Settings

To determine the best compromise for image quality and render time, Chaos Group engineers have measured the performance of V-Ray on thousands of scenes. The results of these tests are the basis for the optimized setup selected as the engine default. They serve as a balanced starting point for a variety of computer graphics productions.

If the default Render Settings do not give the desired result, you can adjust them to fit your needs. The sections below explain which parameter to tweak and how.

Main Parameters (quality vs speed)

Render quality and time are conditioned by the amount of calculations per pixel done and if these calculations are limited in time.

V-Ray continues working until either the maximum number of calculations is reached or when the Progressive image sampler is used when the time limit is reached (whichever comes first).

V-Ray comes with two types of image samplers: Progressive and Bucket. The balance between quality and render time is achieved with the Max. sudivs and Noise Threshold parameters. These are the main parameters controlling the quality vs render time ratio.

Note: For better image quality, increase the Max. sudivs value and/or decrease the Noise Threshold amount. For faster render times, decrease the Max. sudivs value and/or increase the Noise Threshold amount.

The Render Time (min) parameter is available only for the Progressive Image Sampler.

Increasing the Render Time (min) results in better image quality by allowing V-Ray to spend more time sampling the image.

See the animation examples below for illustration:

To limit the progressive rendering to only the amount of time spent on the image, you can set:

• Min. Subdivs to 1
• Max. Subdivs to 10,000
• Noise Threshold to 0.0
• Then, when you set a Render Time value (in minutes), this will be the only criteria for V-Ray to stop sampling the image.

Using a time limit comes handy when rendering animations. Rendering each frame for the same amount of time can help you calculate the time needed to render the entire sequence. For example, with a time limit of 1 minute per frame, a sequence of 60 frames should render for approximately 60 minutes.

My image renders too slow. How to make the rendering faster?

For faster render times decrease the Max. Subdivs parameter for the Bucket or Progressive Image Sampler.

In case you use a Render Time (min) limit, then decrease the time limit value.

Note: Reducing the render time usually produces more noise and results in lower image quality.

In V-Ray for  SketchUp, Rhino and Revit, render time can be reduced by decreasing the Quality slider/preset:

Reducing render time using Quality slider.

My image is too noisy. How to get better image quality?

For better image quality, increase the Max. Subdivs parameter for the Bucket or Progressive Image Sampler.

If you can’t get the desired quality, try decreasing the Noise Threshold parameter a bit.

In case you use a Render Time (min) limit, increase the time limit value to improve the quality.

In V-Ray for Sketchup, Rhino and Revit, render quality can be improved by dragging the Quality slider to a higher-quality preset.

Note: Increasing the sampling limit for higher image quality requires more time to render and in this case, slower render times are expected.

How to approach the Render Settings?

Most of the Render Settings parameters work within different ranges with different sensitivities. You might be tempted to set random values to achieve specific results, but this is rarely the best approach, as extreme values can produce unexpected results.

A more effective approach is to:

How to improve the image quality without slowing down the render?

V-Ray provides a tool for denoising rendered images, called V-Ray Denoiser, that comes with the V-Ray installation. Denoising is a post-rendering process that helps remove noise in the image, without affecting the render time itself.

Since the tool is designed to remove noise, you can use lower-quality render settings and denoise the image after rendering.

To learn more about using the V-Ray Denoiser, visit the denoiser documentation page for: SketchUp, 3ds Max, Maya, Rhino, Revit, Unreal, Cinema 4D, Modo, Nuke, Houdini, Blender.

Note: V-Ray Denoiser also comes as a Standalone Denoise Tool, which can be used outside of the host application and is ideal to process animations.

See Also:

• Can I improve the image quality without starting the render from the beginning?
  Using a combination of the Progressive Image Sampler and the resumable rendering feature can improve the quality of already completed renders - both still images and animations.
  
  If the quality needs improvement, you can pick up the render from where it finished. Resumable rendering allows you to stop and resume without starting the rendering process all over again. 
  
  Note: This feature is only available in V-Ray for 3ds Max and V-Ray for Maya.
  
  More information on Resumable rendering is found here.
  
  
• What are the best render settings for my scene?
  Getting familiar with the basics and learning the balance between image quality and render time will help you choose the best settings for any scene.
  
  
• Other Render Settings
  The information provided in this article covers the basic parameters controlling render time. Other parameters like Displacement and Subdivision settings, as well as Global Illumination also affect the render time and may require adjusting.
  
  
• Recommended Animation Settings
  Rendering of sequences could produce unwanted flickering between frames. Learn how to avoid this by following the steps in this tutorial.