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The number of substeps used for movement blur can be set in the global render options. For simple movement, such as translation and rotation with constant speed, two steps are enough to reconstruct the correct motion. However, if the object accelerates or changes direction during the exposure interval or performs any other kind of non-linear movement, you will need to increase the number of steps until a reasonable look is achieved. The following images illustrate an extreme case where an object moves along a complex path while the shutter is open:
Path in the Maya viewport, for reference. |
With 2 steps, the object follows a straight line |
10 steps are still far from enough to capture |
100 steps are needed to come close to the |
Increasing the number of steps does not usually have a large impact on the rendering performance, but can slow down the export process if the scene has complex relationships which take long to evaluate when the current time is changed.
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Screenshot showing the position of the sphere |
Rendering frame 2 with offset 0. Only movement |
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Changing the offset to 0.5 captures movement |
Offset 1 ends the exposure on the current frame, |
Skinning and Binding
Movement which results from skinning can only be exported as deformation, even if rigid binding is used. In Maya terms, movement blur is only computed based on changes to the attributes of the transform nodes. Anything which is inserted in the construction history of the shape - deformers, tweaks, joint clusters, skin clusters etc. - is seen as deformation by the plug-in.
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The position of the end joint in frames 1 and 2. | |
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Rigid bind. |
Parented to end joint. |
When skinning is used, the movement is exported as deformation. If you set the blur type to Movement Only, no motion blur is rendered. You can notice how the trajectory of the left end of the object is incorrect - it's linear instead of following a curved path, as if the object is shrinking and then enlarging during the motion. In contrast, when the object is parented to the joint, the correct rotation is rendered and Maxwell uses the more efficient movement blur method.
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