This page provides details on using V-Ray's Resumable Rendering feature.
Overview
Resumable rendering is the ability to have incomplete renders resume where they left off from the previous session. The rendering may have stopped due to any number of reasons such as a power failure or having the job bumped off a machine or a render farm, or perhaps you stopped the render manually and want to start from where you left off.
Resumable rendering uses sidecar files for tracking checkpoints. For Bucket sampling, it uses a .vrimg file, and for Progressive sampling, it uses a .vrprog file.
For details on the Resumable Rendering settings, please see the V-Ray Common tab page under the Render Settings window.
A video tutorial is also available here.
How it works
Resumable renders are possible with both Bucket and Progressive Image Sampler types.
With Bucket rendering, an additional .vrimg is written, storing the data of the completed buckets. When resuming the render, V-Ray reads the .vrimg file to determine which buckets still need to be rendered and continues to calculate what is left to complete the image. Another great ability of this feature is that the Light Cache data is saved within the partial image file so that the light cache does not need to be recalculated when the render resumes.
When rendering with the Progressive image sampler, the state of the render is saved to an additional resumable .vrprog file, in a similar way to the .vrimg for Bucket rendering. Setting Autosave Interval (min) from the Image File Output rollout of the Render Settings Common tab (to anything higher than 0) is useful so V-Ray can write out the .vrprog files during rendering, in case the process is unintentionally stopped. However, setting the Autosave Interval (min) value too low (below a couple of minutes for example) may slow the render process.
If V-Ray finds a .vrprog file or a partially completed .vrimg file for the current frame, the rendering resumes from where it left off. If not, V-Ray starts a new render and a resumable file is then saved.
Note that Distributed rendering is also compatible with Resumable rendering.
Render Stopped after 1 passes
Render Stopped after 16 passes
Render Stopped after 64 passes
Workflow
Still Images
- Go to Render Settings window > Common tab > Image File Output rollout and enable the Resumable rendering feature. If using the Progessive sampler, it is highly recommended to enable the Autosave interval (min) by setting it higher than 0. This saves partial files that can be used and helps prevent losing the render progress if Maya crashes and a .vrprog file hasn't been created/updated.
When using the Bucket sampler, the Autosave interval (min) option isn't available.
Bucket image sampler
Progressive image sampler
- Disable the Don't save image (ignored for batch and Cloud) option from Render Settings > Common tab > Image File Output.
If you forget to disabled the option, you will receive an error when you start a resumable render. However, when rendering animations in batch mode, the Don't save image (ignored for batch and Cloud) option doesn't affect the resumable rendering.
- Select an Image Format again in the Image File Output rollout. Any of the possible image outputs can be used for this step.
- Start rendering your image.
The passes calculate for a Progressive render or the buckets begin to drop for a Bucket render. The render can be stopped at any point in time and V-Ray will be able to use the .vrimg or .vrprog files to resume the render later.
If you stop the render and want to resume it on another computer or location, make sure to copy the .vrimg or .vrprog file with the rest of your project so V-Ray can pick up where the render left off. It is not recommended to change Render Settings between stopping and resuming renders. The only settings that are acceptable to change in between stopping and resuming a render are Progressive sampling parameters (Min. subdivs, Max. subdivs, Render time, Noise threshold). Changing settings like the output resolution and render elements causes an error and the render does not resume.
Animations
- Go to the Render Settings window > Common tab > Image File Output rollout and enable the Resumable rendering feature.
- Set the frame range, i.e. Start Frame and End Frame from the Render Settings window > Common tab > Animation rollout.
- Again in the Image File Output rollout, set the Autosave interval (min) if you want. Also if using the Progressive sampler, set the Max. render time to a preferable value depending on how much time you have and the level of quality you need. The Max. render time is located in the Render Settings window > V-Ray tab > Animation rollout.
- Start rendering.
Just like with still images, make sure to copy the .vrimg or .vrprog file with the rest of your project when you stop a render and resume it on another computer or location. Thus, V-Ray can pick up where the render left off. It is not recommended to change Render Settings between stopping and resuming renders. The only settings that are acceptable to change in between stopping and resuming a render are Progressive sampling parameters (Min. subdivs, Max. subdivs, Render time, Noise threshold). Changing settings like the output resolution and render elements causes an error and the render does not resume.
Notes
- Light Cache data is saved in the resumable files, but the Irradiance Map (or any other GI map) is not, and will need to be recalculated when resuming the render. The rendering should still continue from where it was stopped, after the GI data is recalculated.
Enable the Resumable Rendering option before starting a new render, not only when resuming.
- To start a new render, the .vrimg/.vrprog file should be deleted.
- The scene should not be changed between stopping and resuming, except for the Progressive sampling options (Min. subdivs, Max. subdivs, Max Render time, Noise threshold).
- When Test Resolution is enabled, Resumable Rendering is temporarily disabled.