# Motion Stretch

Motion Stretch stretches out your object's points along the path of their movement.

Similarly to Cinema 4D's built in Jiggle deformer, Motion Stretch must be applied as the child of the polygon object you want to deform (it doesn't deform sibling objects). Also, because Motion Stretch looks forward as well as backwards in time to determine how to deform your object's points, it needs to be precached before the effect can be applied - to get started just press the 'Precache' button.

This image shows a sphere and the path it moves along. At the top is the original sphere, in the middle Motion Stretch has been applied with a 'Frame width' setting of 3, and at the bottom is a more extreme example with a 'Frame width' setting of 30.

## Options

1. Automatic cache range - this sets Motion Stretch's cache time range to match the start and end frames of your project's timeline.
2. Cache start / End - with 'Automatic cache range' turned off you can control what time to cache from and to using these settings.
3. Precache - caches the object's current movement, over the times specified using the first 2 settings. Your object must be precached before Motion Stretch will have any effect.
   If you press 'Precache' with multiple Motion Stretch Deformers selected they will all be cached in one run through of the animation, this can save you a lot of time especially for heavy scenes.
4. Clear cache - clears the caches of any selected Motion Stretch Deformers. You'll have to press 'Precache' again to get the effect back.
5. Cache extrapolation - tells Motion Stretch what to do before and after the cached frames. This can be set to either 'Off' to do nothing, or 'Loop' to repeat the cache, handy for any looped animation cycles.
6. Stretch formula - select either Standard (the default) or Toon Blur. The Toon Blur formula works over a smaller time range than the Standard formula (up to 2 frames for Toon Blur, compared to an unlimited number of frames for Standard), but spreads the effect evenly over the frame to more accurately recreate a cartoon motion blur effect.
7. Frame width/Shutter angle - For Frame width (used by the Standard formula (see 5)) - the effect will look half this many frames forwards and half this many frames backwards in time to determine where to stretch your points to.
   For Shutter angle (used by the Toon Blur formula (see 5)) - this reflects the Shutter angle setting used to create standard motion blur effects in Cinema 4D and other 3D applications based on a simulation of a movie camera's shutter (see Rotary disc shutter on Wikipedia for more details). The default of 360° results in a full frame's width of motion blur, 180° would be half a frame, and the maximum of 720° two frames of motion blur.
   Higher values result in a longer stretch, and partial frames are allowed as points will be interpolated between their past and future positions using a spline.
   The amount of movement of each point depends on their normals. Points with normals facing their direction of motion will be stretched forwards in time, those with normals facing away will be stretched backwards in time, and those with normals facing somewhere in between will be stretched less.
   This setting defines the maximum distance in time a point will be moved if its normal faces exactly towards or away from its direction of motion.
8. Squash strength - use this setting to apply a squash effect counter to the movement of your object's points. You can use this for example to help preserve the appearance of the volume of your object.

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