A stretchable virtual fabric depends on the user’s strength of muscle detected by EMG sensors. The fabric patch before being stretched (left). The fabric patch is stretched under muscle tension (right).
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Motivation
Motivation
To create a realistic VR interaction, the implementation of haptic feedback is necessary to sense the object’s properties. While many works have been done on weight and mass distribution perception, the stiffness sensation of soft, thin, and flexible materials such as fabric is lacking. Therefore, we suggest a novel approach to provide a realistic interaction between the user and the virtual fabric.
In this work, we generate the perception of stiffness towards the virtual fabric in the VR environment by combining multi-sensory feedback and muscle strength input. The user’s hand position and the edge of the fabric will be displayed as a virtual offset with tactile feedback as a guideline for the user to make correct hand placement.
Our work makes the following contributions:
• Generating the perception of stiffness towards the virtual fabric in VR by combining multi-sensory feedback and muscle input.
• Suggestion of a novel interaction method to enhance the realistic sensation of objects with elasticity in VR.
Video
Video
Stretchy: Enhancing Object Sensation Through Multisensory Feedback and Muscle Input (2023)
Method
Method
Our approach treats the stiffness of a fabric patch as an elastic spring corresponding to Hook’s Law (F = kx) where k determines the stiffness of the fabric. Two opposite virtual forces due to the fabric’s stiffness Fk are applied when the user stretches the virtual fabric patch.
The muscle force Fm muscle force acts in the opposite direction of the Fk and its magnitude depends on the measured muscle tension. The fabric will elongate at x distance according to the Fm = kx equation as the user stretches. Two modules of Myoware are used to measure muscle activity. Each module is attached to each arm of the user which is connected to Teensy.
The reading data from Myoware are streamed to the Unity via serial IO port and convert the EMG values to force by multiplying the values by 110 N.
where min and max are the minimum and maximum values that can be sent from Myoware sensors while Myodata is the measured value of the user’s muscle tension. For simplicity, Myodata obtains from the average tension of both arms.
The scaling factor is computed and will be used as a value of the max scale constraint which determines the maximum length that the fabric can extend according to the input force.
where k and O are the stiffness and the original length of fabric respectively.
Result
Result
We test our interaction method with three different fabrics with identical sizes (20 cm length and 10 cm width) but different stiffness. There are knit, cotton, and denim and the assigned stiffness value are 100N/m (low), 150N/m (medium), and 300 N/m (high) respectively. The muscle strength was maintained at around 15N.
As shown in the picture, each fabric is stretched and elongated into different lengths. High-stiffness materials such as denim patches are harder to stretch, therefore more force is required to elongate while softer fabric with low stiffness such as knit patches is easy to extend. Our method is not only applicable to virtual fabric but can also be applied to other virtual objects
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