XGen Animation and Motion Blur

This page provides a tutorial on using XGen Animation and Motion Blur with V-Ray.

Overview

Required Steps

You can render animations and motion blurred frames in Maya Interactive Mode or Maya Batch Mode. 

In Maya Batch Mode, an Alembic file is required. You will first have to export the patches for each collection in the scene through the XGen UI to an .abc file (Alembic file). See the XGen in Maya Batch Mode section of the XGen and V-Ray in Maya 2015 and newer page for details on how to do this.

Alternatively, you can force the use of the Alembic file while in Maya Interactive Mode by enabling the Require Alembic File With Exported Patches for Animation option from the V-Ray Settings from the Preview/Output tab of the XGen window:

When the Require Alembic File With Exported Patches for Animation option is enabled, renders will be guaranteed to be the same as in Maya Batch Mode. 

Animation Examples

XGen Attributes

If you make a plane and instance splines on it with a degree of density, you can animate the Length attribute using a texture map (as shown in the XGen General tutorial) with this expression:

$a=map('${DESC}/paintmaps/length');#3dpaint,200.0
$a = 1.0 - $a;
$a = $a - ((25 - $frame) / 24);
$a = clamp($a, 0, 1) * 1.5;
$a

This inverts the length from the map and makes it from 0 to 1.5 depending on the frame (in the 1-24 frame range).

If we render a 24 frame animation (from the V-Ray Common render settings) we get this:

And here is an example of an animated XGen Archive (archive taken from the XGen Archive Primitives page)

Using this expression to the XGen Twist attribute:

$a = ((25 - $frame) / 24);
rand(-180, 180) + sind($a * 360 + 90) * rand(0, 120)

Archives can have animation inside them. For more information, see the XGen Archive Primitives tutorial.

Moving Geometry

You can also have an animation with moving geometry that XGen primitives get instanced onto.

If you animate a sphere to move and rotate for 24 frames, instance XGen splines on it, colorize them with a texture (like shown in the XGen Spline Primitives section) and export the patches for batch render (as explained in the Required Steps section above), the result looks similar to the following:

Motion Blur Examples

To create motion blur, create an animated scene as shown above and enable motion blur from the V-Ray Render Settings as shown below.

Also do not forget to export the XGen Patches for Batch Render, as discussed in the Required Steps section above.

The example below is a motion-blurred scene with a rotating sphere that has red XGen splines instanced onto it.

And here is a motion-blurred scene with an animated Bend U attribute (through keying) with splines.

Notes and Limitations