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. This article will answer why, along with questions such as:
- Why do my render outputs, render times, or levels of noise differ between V-Ray versions?
- When should I expect discrepancies, and how should I deal with them?
- Why should I update to the latest version? What are the benefits?
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How do I find what has changed between release versions?
Why does the latest version render differently?
V-Ray has been around for quite some time. Throughout all these years, the entire computer graphics industry has changed for the better. Various hardware, software, algorithms, and workflows have been depricated, updated or transformed completely.
To keep up with all these changes and chiefly - to benefit from them, V-Ray needs to continuously adapt and evolve. This evolution is inevitably related to changes in the software itself. Such changes improve the software, but sometimes, they also affect its behaviour compared to previous versions. Backwards compatibility is always on our mind, in certain scenarios however, hard change unavoidable.
Take for instance, that there was an issue affecting the way a light is rendered. When the issue is eventually fixed, the result will be more accurate, but different than what it used to be. In such a case, reverting the change by reintroducing the issue will not do anybody good. A similar analogy goes for improved, as well as, depricated features.
What are the benefits of the latest version?
When rendering old scenes with the latest version of V-Ray, the benefits the latest version provides may not be immediately seen, due to a certain difference. First impressions, however, don't reveal everything. Using the latest version provides:
- More accurate results
- Faster render times
- New features
- More intuitive UI
- Less bugs
- Better optimization
It may take a while, but once you spend enough time using the latest version, you won't look back. The sooner you adapt your workflows to the latest version, the faster you'll be able to benefit from it.
Is it possible to force the latest version to render as the previous?
When workflows and pipelines work well, users get so used to them that they don't see reasons to replace them. Using legacy workflows, however, is not recommended. Although, it's possible to make them work, eventually, they will stumble upon even more troubles. Updating your workflows to the Chaos' recommendations is the right approach.
Recommendations
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General
Migrating in the middle of a project to the latest V-Ray version may introduce unexpected challenges that could slow down the project. We recommend completing a project with the same V-Ray version with which it has been started. For fresh projects, it's always better to update.
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When using a library built with an earlier version
When working with the latest V-Ray version, we may stumble upon the fact that our old libraries render differently. In such cases, it may not be convenient to revert to the version with which the library was built.
To preserve the library's appearance, it's a good idea to update it. Note, however, that sometimes, achieving an identical look between old and new versions is not possible. Differences that are caused by a more physically correct look, for example, are not adequately compared. Such behaviour improvements can't be reverted.
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When the latest version seems slower
When releasing a new major version, render speed is one of the most important aspects we monitor. Generally, render times tend to decrease with newer versions; nevertheless, in rare cases, it may so happen that the latest version is slower.
This, however, can be caused by the latest version producing better a better quality image. To get an accurate comparison of render times, it must be ensured that the quality and overall look of the scene are similar. A good start is resetting the render settings to their defaults and tweaking the Image Sampler settings.
When to expect discrepancies?
Generally, breaking changes in the software are introduced between major versions of the software (f.e, V-Ray 6 and V-Ray 7). Seldom do such discrepancies occur between minor versions (f.e. Update 1 and Update 2).
An important note: the farther away the versions' release dates, the greater the differences. For example, more differences are expected between V-Ray 3 and V-Ray 7, compared to V-Ray 6 and V-Ray 7. Hence, why we recommend updating regularly.
What has changed in the lastest version?
The What's New? section of Chaos Docs contains the newest features, changelogs, and a page dedicated to the most important changes introduced in the latest version.
Where to look:
Examples of breaking changes
- 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
- Support for the 3ds Max Color Management
- Metalness rework
For further assistance on the subject, contact Chaos Support.