The Stretch-Engine:
Texas A&M Graduate Thesis
The Stretch-Engine is a prototype tool developed to create exaggeration through squash and stretch by controlling changes a limbs path of motion. This page contains the test and results of exaggerating animations, based on realistic actions, using the prototype. There are three tests with each focusing on more complex exaggerations. The first is based on a boxer knocking out their opponent, the second is of a baseball player hitting a home-run, and the third is a section of a parkour compilation.
The Stretch-Engine was designed to work within a 3D animation software, Autodesk's Maya. For the best performance it is recommended to run the Stretch-Engine within Maya 2015 and newer versions, because script development began with the 2015 version and then moved to later versions as the project developed. You can download the files needed to install the Stretch-Engine here: stretchEnginePackage
Animation Test 01 - Boxing
The first test focuses on one part of the body, the left arm, to show that the tool can handle a simple change in limb size. The left arm will be scaled to exaggerate the straight punch before throwing their right hook.
Simple Exaggeration
In this example the arm is scaled by a factor of 2. The result is a length twice as long as the original length. In this version all dimensions of the motion path are scaled, scaling the lead up as well.
Refined Exaggeration
In this example the arm is scaled by a factor of 3. The result is a more intense punch then in the simple test. In this version the Y dimension is not scaled, keeping a similar lead up to the original animation but now with the change in limb length.
Animation Test 02 - Baseball Swing
The second test focuses on both of the characters arms to show that the tool can handle changes to a pair of limbs. To exaggerate the action, both arms are scaled during the swing until the moment of impact with the ball.
Simple Exaggeration
In this example, both arms are scaled by a factor of two and all dimensions are scaled without any adjustments. The result is slight separation between the arms near the end of the action due to the change of scale increasing the distance between the limbs.
Refined Exaggeration
In this example, the arms are scaled by two but an easing effect is added to the action. This creates a more sudden change in length near the end of the swing. Also, the left arm's exaggerated path is manually adjusted to keep the bat within the hand throughout the action, fixing the separation.
Animation Test 03 - Parkour
The third test focuses on stretching multiple limbs of the body. For this particular animation there are two areas where stretching occurs, during a leap towards a ledge and a landing towards the final platform. During the leap the arms and the legs are stretched while during the landing all parts of the body are stretched.
Simple Exaggeration
In this example, all limbs are scaled by 2.
During the leap, the stretching of the legs are reversed so they stretch away from the direction of motion while the arms stretch towards the direction of motion. A scale of 2 creates too large a change in length for the area, resulting in the legs stretching passed the original launch position and the arms stretching passed the ledge.
During the fall the arms, neck, and torso stretching is reversed to stretch away from the ground. similar to the leap the change in length is too large resulting in the limbs stretching to far for the area they are required to travel within.
Refined Exaggeration
In this example all limbs are scaled by 1.5.
For the leap, a scale of 1.5 keeps the legs from stretching passed the original launch position but still create an exaggeration in the action. The arms also stretch as if to reach for the ledge but do not pass the ledge before making contact.
During the landing the arms, neck and torso do not stretch passed their position before falling in space. Also the middle controller along the torso is adjusted to better match the new shape of the spine.