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Digital Sleight-of-Hand: Changing Prop Parenting in Animations

For use with Poser 7 as well as previous Poser versions back to 4

One of the most useful features for animators is the ability to attach or "parent" a prop to any given object. The parent object can be anything from another prop to a body part like the head or a hand. Parenting a prop makes it behave as part of the parent object removing the need to keyframe the prop separately thereby avoiding the subtle slips and shifts which can make an animation look unrealistic.Digital Sleight-of-Hand: Changing Prop Parenting in Animations

One of the most useful features for animators is the ability to attach or "parent" a prop to any given object. The parent object can be anything from another prop to a body part like the head or a hand. Parenting a prop makes it behave as part of the parent object removing the need to keyframe the prop separately thereby avoiding the subtle slips and shifts which can make an animation look unrealistic. Unfortunately the state of an object's parentage cannot be animated, and hence once parented a prop will remain attached to its parent for the entirety of the animation.

With only a little bit of trickery it is possible to create the illusion of a prop changing parentage. Like many sleight-of-hand magic tricks we will use more than one prop and manage what is presented to the audience.

Here I have loaded the mannequin figure from the "Additional Figures" library and also added the same "Fedora" prop twice.

Each hat has been positioned relative to its parent, renamed using the Properties tab of the Parameter Dials palette for clarity, and parented to the desired object by clicking the Set Parent button also found on the Object Properties tab.

Further, the hat parented to the head has been set to display as a wireframe by selecting Display menu > Element Style > Hidden Line. Element Display Style can also be chosen from the Preview Style popup found by default in the lower left corner of the Poser workspace. Using different display methods will be useful in providing a visual distinction between the two props while setting up the animation.

By default most of Poser's keyframes are set to interpolate the value between them, meaning that the position of an object will change gradually from one keyframe to another later in time. This is useful for creating the smooth motions required for animating a moving figure, but also means that other parameters such as Scale will also change gradually. This would result in a hat that appeared to slowly shrink from 1 to frame 30. Instead we want the hat in the hand to disappear instantly. This can be accomplished with the Constant Section interpolation method. This option simply holds a parameter's value until another keyframe is encountered.

For this animation the interpolation methods for both hats was set to Constant Section so changes would occur instantaneously. The method was changed by selecting the keyframes for the objects and clicking the gray " - " button in the upper right of the Animation palette.

Next, the character was animated bringing the hat in the hand up to the head. Ultimately the position of the hat in the hand must be virtually identical to the position of the prop to be swapped. Utilizing the two display styles helps with the process of fine positioning of the objects.

The motion of placing the hat on the head would take approximately one second, so in a 30fps animation the keyframes animating the arm and hand were created at frame 30. It is also at this point that the hats will be switched for the final animation.

Once the hats were aligned at the critical keyframe the "Fedora_Hand" prop is made invisible. The simplest way to accomplish animating this visibility change utilizes a change of Scale from 100% to 0% in. Since the interpolation is set to Constant the hat will disappear at this point.

I then returned to the beginning of the animation to make the hat on the head invisible for the first part of the sequence using the same technique. I remembered to set its Display Style to the document settings.

To finish off the sequence I applied a generic walk using the Walk Designer from frame 31 through 90 allowing the figure to transition for 15 frames.

The resulting effect is pretty cool. Note that even if the positions of the props aren't identical at the switch point, the transition takes place in 1/30th of a second and the objects are already moving. It is basically impossible to tell that there are two props utilized in the scene. Pretty neat, huh?

You can take a look at the rendering or download the .pzz file to inspect the scene file yourself.

Take care,

Steve