VFX Studios Tutorials - Rendering a Fly-Through Animation with V-Ray and Backburner using GI

Rendering a Fly-Through Animation with V-Ray and Backburner using GI

V-Ray is an incredibly powerful rendering engine, but with it comes long render times - especially when rendering animations. This guide is written to help you minimise the waiting time by using network rendering in 3ds Max. This guide can also be applied to non-network rendering by simply unticking the "net render" box in the common tab of render settings.

This tutorial is very useful and shows you how to set up the light cache and irradiance map properly, but it's missing a few vital steps that I will go through in detail.

The first thing to note about using Global Illumination is that you can't use the 'incremental add to map' methods when rendering on multiple machines. (Stick with me if you don't understand that, there are pictures to show what I mean.) This is because only one pc can save the file at one time, so multiple machines simply overwrite each others data.

The solution to this is relatively simple to set up:

Firstly the Light Cache needs to be rendered and saved to disk.
Secondly the Irradiance Map needs to be rendered and saved to disk.
Thirdly, the final animation can be rendered pointing to these two files.

Luckily, this can all be automated using Backburner.

Setting up the Light Cache

Even though it's an animation you are rendering, set the time outpout to a single frame. The Light Cache will produce a file from your timeline, not your time output. Make sure your timeline is set to the frames you want to render.

Untick "Save File" as this is not necessary yet.

Tick "Don't render final image" as we are only rendering the light cache at the moment.

Both Primary and Secondary GI Engines must be set to Light Cache.

Set the mode to "Fly Through", tick the boxes highlighted and choose a location to save the light cache file.

Once all settings are correct, click render. (If you are network rendering remember to tick "Net Render")

Click "Advanced" on the network render window that appears, and then select "Enable Limit". This will make sure only one render server is processing the light cache.

Setting up the Irradiance Map

Select "Active Time Segment" (or range if you only want to animate a small part) and make sure "Save File" is unticked as this is unneeded for the time being.

Choose to render every 10th frame for the IR map, any more is usually not needed unless the camera is moving very quickly. The first frame will render relatively slowly, but the frames after that will render much quicker due to "multiframe incremental" mode being selected.

Make sure this tick box is still selected.

Set the primary engine to Irradiance map, and the secondary to Light Cache.

Set the mode to "multiframe incremental" and choose a location to save the file. (This must be a shared network location if you are network rendering)

The IR Map will build on the already computed light cache. Choose "From File" and select the location where you saved the light cache file.

It doesn't matter if the light cache file hasnt finished yet as this job will not start until the previous one has completed.

Click "Render" (Remembering to click net render if using backburner)

Ensure the server limit is still ticked and set to 1.

IMPORTANT: In order for this file to not start rendering until the previous light cache file has completed, click "Dependencies" on the network render window and add the previous light cache job to the list. If you ever forget to do this, you can simply add a dependency using Backburner's Queue Monitor by right clicking on the job and clicking "Select Dependencies".

Setting up the Final Render

Select the range of frames you want to render. In this case I am rending all frames from 0 to 125.

Make sure you render every single frame by choosing "1" in the "Nth Frame" box.

Finally, save your image sequence to your desired location (Again, this needs to be in a networked location if using backburner).

Untick "Don't Render Final Image"

Set the IR Map and Light Cache to load from the files made in the previous renders. This job will later be set so that it does not start until those files have been completed.

Untick "Enable Limit" so that all the servers can render off the final animation.

IMPORTANT: In order for this file to not start rendering until the previous light cache and IR Map has completed, click "Dependencies" on the network render window and add the previous two jobs to the list. If you ever forget to do this, you can simply add a dependency using Backburner's Queue Monitor by right clicking on the job and clicking "Select Dependencies".

Your animation should now be set up to render on Backburner using V-Ray GI. This sounds quite complicated at first, but it's easy to set up, reduces render time substantially and stops that horrible GI flicker if you were to calculate GI on each frame.

Thank you for reading this, and I hope you will find it useful.

Tutorial written by Tim Hawker. If you have any questions please leave a comment.