Just adding an update on the fluid surface motion blur. The previous motion blur rendering setup is no longer recommended and contains a legacy geometry node. Legacy nodes will eventually be removed before Blender 4.0 and they also cannot be added as nodes in more recent versions of Blender 3.0.
I have updated the setup to use the newer Geometry Nodes ‘Attributes and Fields’ workflow. The example file can be found in the Experimental Builds package and requires an installation of the most recent FLIP Fluids experimental version (current: v9.1.3, 03-NOV-2021).
The example file can also be downloaded here: motion_blur_rendering_example.blend (1.2 MB)
Notes from the example file:
This example .blend file demonstrates a quick set up for how to render
the FLIP Fluids addon liquid surface with motion blur. This example file
is intended to be used with builds of Blender 3.0 on the date of or later
than October 31st 2021.
Blender 3.0 adds a feature that allows for the FLIP Fluids surface to be
rendered with realistic motion blur, something that was previously not
possible. Whitewater motion blur rendering is not yet possible, but will
hopefully be added by the Blender developers at a later date.
This set up uses a simple Geometry Node network to transfer the FLIP Fluids
addon velocity data attribute into Blender's own velocity attribute, which
can then be used by the Cycles renderer for motion blur rendering.
How to use this example file:
- Bake the fluid simulation
- Render an image or an animation
- Note: motion blur rendering is not displayed in viewport render
- The node network and data values can be viewed by selecting the
fluid_surface object. The GeometryNode modifier can be view in the
fluid_surface modifiers tab.
How the node set up works:
- The FLIP Fluids addon stores its own custom surface velocity vectory data
into the attribute named 'flip_velocity'.
- A vector math node scales this vector and stores the result into Blender's
internal velocity attribute which is named 'velocity'.
- The amount of motion blur can be optionally scaled by adjusting the 'Blur Scale'
value in the fluid_surface modifiers tab.
- The geometry node attribute data values can be viewed in the spreadsheet window
when the fluid_surface object is selected.
Additional notes:
- These notes may be helpful for if you want to set up motion blur rendering on a
new scene.
- By default, the option to generate the 'flip_velocity' attribute is hidden. This
option can be unhidden by enabling the 'Developer Tools' option in the FLIP Fluids
preferences menu. Afterwards, the option to generate velocity attributes can be
enabled the FLIP Fluid Surface panel.
- Generating velocity attributes is still considered an experimental feature due to
a bug in Blender that can cause render crashes
(https://developer.blender.org/T88811). Until this bug is fixed, a workaround is
to render from the command line.
- Motion blur rendering is only supported in Cycles. Motion blur rendering must be
enabled in the Render Properties menu as well as on the fluid_surface Object
properties menu.
- The 'flip_velocity' attribute is added as a Group Input node in the node network.
The input attribute name (flip_velocity) is specified in the GeometryNode modifier.
- Blender's 'velocity' attribute is added as a Group Output in the node network.
The output attribute name (velocity) is specified in the GeometryNode modifier.
Here’s an example animation using motion blur, created for Halloween!
