Triggermuscle: Exploring Weight Perception for Virtual Reality Through Adaptive Trigger Resistance in a Haptic VR Controller

Abstract

It is challenging to provide users with a haptic weight sensation of virtual objects in VR since current consumer VR controllers and software-based approaches such as pseudo-haptics cannot render appropriate haptic stimuli. To overcome these limitations, we developed a haptic VR controller named Triggermuscle that adjusts its trigger resistance according to the weight of a virtual object. Therefore, users need to adapt their index finger force to grab objects of different virtual weights. Dynamic and continuous adjustment is enabled by a spring mechanism inside the casing of an HTC Vive controller. In two user studies, we explored the effect on weight perception and found large differences between participants for sensing change in trigger resistance and thus for discriminating virtual weights. The variations were easily distinguished and associated with weight by some participants while others did not notice them at all. We discuss possible limitations, confounding factors, how to overcome them in future research and the pros and cons of this novel technology.

Continuous VR Weight Illusion by Combining Adaptive Trigger Resistance and Control-Display Ratio Manipulation

“…Several introduced techniques rely on either modifications of air resistance [25,51], elastic properties [45], weight shift [39,50], absolute weight change [7], or both [30]. Most recently, researchers proposed Triggermuscle, a VR controller adapting the resistance of its trigger to simulate differences in virtual weight [43]. While this haptic interface has been shown to successfully convey different weights, the weight illusion did not take effect for several participants -motivating this work on improving the concept through an additional rendering of a virtual weight simulation.…”

“…Adaptive Trigger Resistance During Grasping To provide users with a haptic weight cue while grasping a virtual object (phase 1), we adapt the resistance of the VR controller's trigger button. For this, we use a haptic VR controller identical in construction to Triggermuscle [43] (see Figure 2 (left)). The haptic feedback is informed by how humans modulate their grip forces according to the weight of a grasped object: The heavier a virtual object, the higher the trigger resistance, i.e., the more force needs to be applied to pull the trigger and to prevent the virtual object from falling down.…”

“…Along with an 11.1 V lithium polymer battery and a battery eliminator circuit (BEC) component, the MCU is carried in a small bag on the user's back and connected to the controller's bottom via cable. See [43] for further specifications.…”

“…Participants wore the HTC Vive Pro Eye head-mounted display (HMD) and used the haptic VR controller Triggermuscle [43], held like an unmodified HTC Vive controller. The resistance of the trigger was only adapted in the conditions TR ONLY and TR+CD.…”

“…However, approaches with only minimal adaption (or none) of existing VR controllers constitute an opportunity to introduce haptic weight perception to the consumer market. Recent work [43] proposed a haptic VR controller Triggermuscle that adapts the resistance of the trigger button to simulate different levels of weight during the interaction in VR. The adaptation of resistance provides cutaneous cues [24,28] by mimicking the variations in grasping forces encountered when interacting with physical objects of different weights.…”