Setting up Motion Blur in Cycles and Eevee for Blender

By default, Blender animations are rendered as a sequence of completely still images. While this is ideal for stop-motion and time-lapse videos, it is unrealistic because fast-moving objects appear blurred in the direction of motion, both in a movie frame and in a photograph taken with a real-world camera. In today’s article, iRender will walk you through setting up Motion Blur in Cycles and Eevee for Blender. Let’s get started!

Below is an example of the motion blur effect in Blender:

Position: Controls when the shutter opens in relation to the current frame.

• • • Start on Frame: The shutter is starting to open at this frame.
    • Center on Frame: It is fully opened at this frame.
    • End on Frame: It is fully closed at this current frame.

Shutter: This is the time (in frames) between when the shutter begins to open and it fully closes. For example, when the shutter time value is 1.0, the motion blur effect blurs over the length of 1 frame.

Rolling Shutter: This setting option creates a Rolling Shutter effect.

• • • None: This means no rolling shutter effect.
    • Top-Bottom: Meaning rendering the rolling shutter effect from the top to the bottom of an image.

Rolling Shutter Duration: This controls the balance between the pure rolling shutter effect (when the value is 0) and the pure motion blur effect (when the value is 1).

Note: If a scene contains particles or another physics system, make sure to bake them before rendering; otherwise, you may not achieve correct or consistent motion blur. To control motion blur, each object has its own settings. These settings can be found in the Properties’ Object tab. For further details, see the object setting here.

Shutter Curve: The shutter curve defines how the shutter opens and closes. The X axis represents time, whereas Y values of 0 represent totally closed shutters and Y values of 1 represent fully opened shutters. When the shutter opens and closes instantly, this is the default mapping.

Some Limitations you need to know about motion blur in Cycles:

• • • Deformation motion blur does not operate on objects that are set to Auto Smooth.
    • Orthographic cameras do not provide camera motion blur.
    • Motion blur does not take into account the movement of Lights.

Position: Controls when the shutter opens in relation to the current frame.

• • • Start on Frame: The shutter is starting to open at this current frame.
    • Center on Frame: It is fully opened at this frame.
    • End on Frame: It is fully closed at this current frame.

Shutter: This is the time (in frames) between when the shutter begins to open and it fully closes.

Just like Cycles, the position and shutter settings are the same as those in Cycles renderer. Next, we move to the next setting options in Eevee.

Background Separation: The post-process blur uses this to avoid blurring the background over the foreground. Lower values reduce the amount of background bleeding onto foreground elements.

Max Blur is the maximum blur distance that a pixel can cover. When set to 0, the post-process blur is disabled and just the accumulation blur is used. Please note that high values of maximum blur may also reduce the quality. 

Eevee utilizes a quick post-process vector blur with a vector motion pass. Using pixel velocity, this blurs the image over three time steps. This technique is rapid and provides clean gradients, although problems can arise at object borders or if the motion is locally too complex; for example, if there are many vector variations in a small area. This method applies random sampling, and the amount of noise is proportional to the sample count found in Properties > Render > Sampling > Render Samples.

Steps: This setting determines how many steps the accumulation blur takes and consequently its accuracy. More steps equal a longer render time. Note that when using multiple time steps, the render sample count is rounded up to the next multiple steps to ensure that samples are distributed evenly across steps. 

Eevee renderer divides the render into multiple time steps and accumulates the result, known as Accumulation Motion Blur. This approach is accurate, although it takes many steps to achieve clear gradients. This is used in conjunction with the post-process blur to handle inter-step gaps. Each step equates to a full scene re-evaluation and can add a significant amount of cost to the render time. By adding more steps, you can also reduce the Max Blur settings because the post-process blur must cover a smaller distance.

Below are some pictures demonstrating how each setting creates the motion blur effect: 

Source: docs.blender.org

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Reference source: Blender Documentation