How to render flicker free animations with V-Ray

30.04.2016
Gareth Williams Founder & CEO
Home >Blog >How to render flicker free animations with V-Ray

Easy to Follow | Animation Basics

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At YellowDog we do a lot of 3D rendering. One of the hardest things to get right, especially when you’re using many different machines to do the rendering of an animation, is how do you ensure every frame has exactly the same lighting when using Global Illumination, or GI. Given the complex mathematics and sampling used by render engines to calculate the lighting, it’s quite common for flickering and other artefacts to appear in the render.

For scenes where you have moving objects, and are being rendered with V-Ray, the best solution we’ve found is to use time-interpolated irradiance maps. These work by blending samples from several irradiance maps which helps ensure there is no flickering or differences between the frames. It’s also a lot faster than using brute force rendering.

There are two steps needed to render the animation:

  1. Create the irradiance maps for each frame of the animation.
  2. Render the final animation.

Step 1

Once you’ve opened your scene, the V-Ray settings for the first step are:

Setting Value Reason
GI On Enables Global Illumination for the scene
Primary Bounces Engine Irradiance Maps
Secondary Bounces Engine Light Cache
Irradiance Map Preset Medium animation
IM Subdivs 50
Interp samples 20 The number of GI samples from each irradiance map used to interpolate the GI at any point
Use Camera Path Checked Helps to reduce flickering when the camera moves
Mode Animation (prepass)
Save Choose a directory to store the irradiance map
Don’t delete Checked
Autosave Checked and Choose a directory to store the irradiance maps
Light Cache Subdivs 1200
Sample size 0.15
World Scale Checked This is the right mode for animations where the camera is moving.
Use Light Cache for Glossy Rays Unchecked If you check this, you will need to keep Light Cache as your Secondary Engine in Single Frame mode for step 2
Use Camera Path Checked Helps to reduce flickering when the camera moves
Mode Single Frame
Animation start frame Playback start -2 Ensures all the irradiance maps needed for every frame are calculated. If you start from the beginning of the playback, the first few frames will be noisy.
Animation end frame Playback end +2 Ensures all the irradiance maps needed for every frame are calculated. If you finish at the end of the playback, the last few frames will be noisy.

Step 2

Now render the whole animation.

You should see an individual irradiance map for each frame appear in the directory you specified.

Once this is done, you’re now ready to render the final animation. The settings for this are:

Setting Value Reason
GI On Enables Global Illumination for the scene
Primary Bounces Engine Irradiance Maps
Secondary Bounces Engine None The light cache information has already been generated and stored in the first step
Irradiance Map Preset Medium animation
IM Subdivs 50
Interp samples 5 Decreased as several irradiance maps are being used for rendering. If this doesn’t look right, you can increase it. You may have to go to 10-12 for interior animations although this increases render time.
Interp frames 2 How many irradiance maps are used for rendering one frame of animation.
Use Camera Path Checked Doesn’t have any effect any more.
Mode Animation (rendering)
Save Choose a directory to store the irradiance map
Don’t delete Checked
Autosave Checked and Choose a directory to store the irradiance maps
Animation start frame Playback start
Animation end frame Playback end

And press render.

We’ve found this method produces great results every time.

Happy rendering!

 

Watch the 2018 update to rendering V-Ray flicker free here:
Categories:
CGI

CGI

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