Impact force is common haptic feedback on virtual reality (VR) controllers, such as hitting objects with weapons or rackets. It applies to different points of application of force (PAFs) and directions in varied scenarios. For example, using weapons with different shapes, e.g., a sword and a pickaxe, using a weapon in different ways, e.g., stabbing and slashing with a sword, or a ball flying and hitting a racket in different directions cause different PAFs and/or force directions. Therefore, to achieve realistic VR experiences, rendering dynamic PAF and force direction is essential. Although previous works have proposed the concept of dynamic PAF, the PAF is only in a limited space and without dynamic force direction. Therefore, we propose a controller, transPAF, to render omnidirectional impact feedback with dynamic PAF all round the controller for versatile VR scenarios. transPAF consists of a controller, a semicircular track, a linear track, and an impactor, which are all rotatable. The impactor can move to any position in a sphere, which means the whole 3D space all round the controller, and rotate in any direction. Therefore, dynamic PAF and force direction are achieved and independent to each other. We conducted a just-noticeable difference (JND) study to understand users’ distinguishability in position and direction, separately. A VR experience study was further performed to verify that feedback from transPAF with dynamic PAF and force direction enhances the VR experiences and demonstrate some applications for transPAF.

Haptic feedback not only enhances immersion in virtual reality (VR) but also delivers experts’ haptic sensation tips in VR training, e.g., properly clamping a tenon and mortise joint or tightening a screw in the assembly of VR factory training, which could even improve the training performance. However, various and complicated manipulation is in different scenarios. Although haptic feedback of virtual objects’ shape, stiffness or resistive force in pressing or grasping is achieved by previous research, rotational resistive force when twisting or turning virtual objects is seldom discussed or explored, especially for a wearable device. Therefore, we propose a wearable device, ELAXO, to integrate continuous resistive force and continuous rotational resistive force with or without resilience in grasping and twisting, respectively. ELAXO is an exoskeleton with rings, mechanical brakes and elastic bands. The brakes achieve shape rendering and switch between with and without resilience modes for the resistive force. The detachable and rotatable rings and elastic bands render continuous resistive force in grasping and twisting. We conducted a just noticeable difference (JND) study to understand users’ distinguishability in the four conditions, resistive force and rotational resistive force with and without resilience, separately. A VR study was then performed to verify that the versatile resistive force feedback from ELAXO enhances the VR experiences.