Discrepancies between V-Ray versions

Updated June 16, 2023 08:31

This article explains why some projects created with older versions of V-Ray render differently with later versions.

Overview

If you are a long-time V-Ray user, you’ve probably noticed that some of the projects you built with earlier versions of V-Ray render differently with later versions. Sometimes the differences are unnoticeable, other times they are quite obvious. You may also notice discrepancies in render times, memory consumption, etc.

This article answers questions such as:

Why do my render outputs, render times, or levels of noise differ between V-Ray versions?
When I could expect such discrepancies and how do I deal with them?
Why should I update to the latest version? What are the benefits?
How do I find what has changed between release versions?

Why does the latest version of V-Ray render differently?

V-Ray has been around for quite some time. Throughout all these years, many areas have been tremendously improved including hardware, software, algorithms, workflows and pipelines, the overall computer graphic industry. To keep up with all these changes and benefit from them, V-Ray needs to continuously adapt and evolve. This evolution is inevitably related to changes in the software itself.

These changes make the software better, but, in some cases, they also affect how it behaves compared to previous versions. We always try to minimize changes that would affect the render output but, on some occasions, they can't be avoided. For example, imagine there was a bug in an older version of the software that affects the way light is rendered. When this bug is fixed, it shows a different but more accurate result in the later version. In this particular case, there is no way of reverting the change back because this would deteriorate the software overall.

Here are a few more examples that can potentially cause discrepancies between versions:

Fixed bugs
Improved features
Removing obsolete features

What are the benefits of the latest versions compared to the earlier ones?

Sometimes the benefits of a later version rendering old scenes and showing discrepancies might not be immediately seen. This first impression however doesn't reveal the full picture. Latest versions always have multiple benefits compared to the previous ones, including (but not limited to):

More accurate results
Faster render times
New features
More intuitive UI
Less bugs
Better optimization

It might take some time to see the benefits, but once you spend some time with the latest version, you won't look back. The sooner you start using the latest version and adapt your workflows, the faster you’ll be able to benefit from it.

What do we recommend to avoid discrepancies between V-Ray versions?

Migrating in the middle of a project to a later V-Ray version may introduce unexpected challenges that could slow down the project. That’s why it’s recommended to complete the project with the same version it has been started with and start new projects with the later version.

What do we recommend if using the earlier version is not an option?

In some cases using the earlier version of the software may not be an option. A typical case would be a library of scenes built with a previous version of V-Ray, that needs to be used in later projects created with the latest version of V-Ray. In such cases, it is not convenient to use the earlier version of the software. If you want to preserve the library appearance, it is a good idea to update it. Simply changing the material or lighting setup will do the trick.

Note: Sometimes achieving an identical look between earlier and later versions is not possible. Differences caused by the accuracy improvement of the render are inaccurately compared. Such behavior can't be reverted.

What to do if the latest version of the software renders slower compared to the earlier one?

Render speed is one of the most important aspects we constantly monitor, especially when we release a new major version. Generally, render times decrease with time, so the latest version tends to be faster than the previous one. In some rare cases, however, you may notice the latest version renders more slowly. If so, we recommend starting from scratch by resetting render settings and tweaking the Image Sampler to get similar results as with the previous version.

Sometimes, later versions’ render times are higher, but the cause for this is that it produces a better quality, less noisy image. In order to properly compare render times between both versions, we need to ensure that the quality and overall look is the same.

Is there a way to force the later version to get the same result as the previous one?

This is usually the first thing to come to mind when seeing discrepancies between versions. When workflows and pipelines work well, people get so used to them that they don’t see any reason to replace them. Using legacy workflows in a later version, however, is not recommended. Even though you can make them work they will eventually break apart and introduce even more troubles. The right approach here is to update the workflows to the recommended ones by Chaos. The sooner you do it, the better. If you need any assistance on that matter don’t hesitate to reach the Support team.

When to expect discrepancies?

Generally, breaking changes in the software are introduced between major versions of the software, f.e. V-Ray 5 vs V-Ray 6. Seldom such discrepancies between minor versions, such as V-Ray 6, update 1 vs V-Ray 6 update 2, occur.

Another important thing to note is that the farther away the version release dates are, the greater the discrepancies between them are. This means that it’s expected to observe more differences between V-Ray 3 and V-Ray 6 compared to V-Ray 5 and V-Ray 6. This is why we recommend updating to the latest version of the software at the earliest opportunity.

How to find what is changed between V-Ray versions?

In the Chaos Docs portal’s What’s New section for each product you can find all the changes made in every version of the software. In the same section, you can also find a page gathering the most important breaking changes introduced with the latest version of the software. For example:

Examples of changes that may affect the render output of projects created with previous versions.

Adaptive lights
Consistent render elements
Reflection glossiness
Removed High Glossiness parameter (available in V-Ray 3.x)
Removed Clamp and Sub-pixel mapping parameters (available in V-Ray 3.x)
Removed GI Multipliers
Removed Subdivisions and Noise threshold for DMC sampler
V-Ray Lights: Affect Reflection/Specular behaves in a different way.
Additive invisible lights
Support for multiple V-Ray Dome lights
“Visible to GI” is removed from V-Ray Object Properties and will render as OFF for old scenes
“Glossy Fresnel” option in VRayMtl is no longer in the UI, old scenes with Glossy Fresnel=OFF will be forced to render with Glossy Fresnel=ON in V-Ray 6

Conclusion

This article explained why different versions of V-Ray may behave differently and what you can do if you notice such behavior. If you need further assistance on the subject, don’t hesitate to reach Chaos Support.