Controller-free hand tracking for grab-and-place tasks in immersive virtual reality: Design elements and their empirical study

Hand tracking enables controller-free interaction with virtual environments, which can, compared to traditional handheld controllers, make virtual reality (VR) experiences more natural and immersive. As naturalness hinges on both technological and user-based features, fine-tuning the former while assessing the latter can be used to increase usability. For a grab-and-place use case in immersive VR, we compared a prototype of a camera-based hand tracking interface (Leap Motion) with customized design elements to the standard Leap Motion application programming interface (API) and a traditional controller solution (Oculus Touch). Usability was tested in 32 young healthy participants, whose performance was analyzed in terms of accuracy, speed and errors as well as subjective experience. We found higher performance and overall usability as well as overall preference for the handheld controller compared to both controller-free solutions. While most measures did not differ between the two controller-free solutions, the modifications made to the Leap API to form our prototype led to a significant decrease in accidental drops. Our results do not support the assumption of higher naturalness for hand tracking but suggest design elements to improve the robustness of controller-free object interaction in a grab-and-place scenario

The immersive virtual memory task: Assessing object-location memory in neurological patients using immersive virtual reality

Memory for object locations in proximity is an essential aspect of everyday activities and has high clinical relevance. Immersive Virtual Reality (VR) has the potential to bridge the gap between the experimental control of laboratory conditions and reliable predictions of functional abilities. We developed the immersive Virtual Memory Task (imVMT), a neuropsychological assessment tool for spatial memory that combines gesture-based natural hand interaction and a head-mounted display. Our aim was to investigate the imVMT task characteristics, to validate the imVMT regarding the underlying cognitive processes, and to evaluate its applicability and feasibility in the clinical context in a sample of thirty-five patients with various neurological disorders and functional deficits. We further aimed to assess object-location memory in a small-scale virtual environment. Our results show that task difficulty can be efficiently manipulated by increasing the number of objects to memorize and rotation angle against the encoding perspective. We demonstrate construct validity as our primary outcome measure was significantly related to spatial memory performance in conventional neuropsychological tests. The imVMT was highly feasible and received high ratings for usability. The imVMT represents an ecologically relevant and valid VR task for assessing object-location memory in a wide range of neurological patients

Effect of Atmosphere in a Foundry Mould on Casting Surface Quality

Changes of gas pressure in the moulding sand in the zone adjacent to mould cavity were analysed during pouring of cast iron. No significant effect of pressure on the surface quality of castings was observed. In the second series of tests, the concentration of hydrogen in the gas atmosphere was measured. It has been found that the value of this concentration depends on metal composition and is particularly high in cast iron containing magnesium. This is due to the reduction of water vapour with the element that has high affinity to oxygen. The presence of hydrogen causes the formation of gas-induced defects on the casting surface

Atmosfera gazowa występująca podczas wykonywania odlewów w technologii pełnej formy

A test mold was designed to investigate the full mold process. Pressure changes in a gap developing between the pattern made of foamed polystyrene and the raising column of liquid alloy were determined. Studies were conducted pouring molds with cast iron and with AK11 silumin. It was found that pressure is significantly higher in the case of cast iron, due to a higher rate of pattern decomposition and more advanced dissociation of hydrocarbons. The increase in pressure was observed to have no significant effect on changes in the pouring rate as it was compensated by higher metallostatic pressure. The increase of pressure occurs immediately after the start of pouring, it reaches a maximum and then stabilizes or decreases smoothly as a result of the drop in metallostatic pressure. The temperature of pouring has a significant effect on the decomposition rate of hydrocarbons evolving from the metal. During pouring of cast iron, the presence of hydrogen was revealed. It was particularly evident across the gas-permeable coating, where the concentration has exceeded 40%. Hydrogen precipitation was accompanied by an evolution on the casting surface of considerable amounts of pyrolytic carbon. It was found that gases forming in the gap were totally free from oxygen.Zaprojektowano próbną formę do badania procesu full mold. Określono zmiany ciśnienia w szczelinie powstającej pomiędzy styrodurowym modelem a podnoszącym się ciekłym stopem. Badania prowadzono przy zalewaniu form żeliwem oraz siluminem AK11. Stwierdzono, że ciśnienie to jest znacznie wyższe w przypadku żeliwa, co wynika z większej szybkości rozpadu modelu i dalej posuniętej dysocjacji węglowodorów. Wzrost ciśnienia nie powoduje jednak istotnej zmiany szybkości zalewania, ponieważ jest on kompensowany wyższym ciśnieniem metalostatycznym. Wzrost ciśnienia następuje bezpośrednio po rozpoczęciu zalewania, osiąga ono maksimum poczem stabilizuje się lub łagodnie maleje w wyniku zmniejszania ciśnienia metalostatycznego. Temperatura zalewania ma istotny wpływ na stopień rozpadu, wydzielających się z modelu węglowodorów. Przy zalewaniu żeliwa stwierdzono obecność wodoru. Jest ona widoczna zwłaszcza po drugiej stronie powłoki gazoprzepuszczalnej gdzie stężenie sięga powyżej 40%. Wydzielaniu wodoru towarzyszy wydzielanie się na powierzchni odlewu, znacznych ilości pyrolitycznego węgla. Stwierdzono, że gazy tworzące szczelinę są całkowicie wolne od tlenu

Studies of Gas Atmosphere Near the Metal-mould Interface During Casting and Solidification of Ductile Iron

In sand moulds, at a distance of 3 mm from the metal- mould interface, the sensors of temperature, and of oxygen and hydrogen content were installed. Temperature and the evolution of partial gas pressure have been analysed in moulds bonded with bentonite with or without the addition of seacoal, water glass or furan resin. Moulds were poured with ductile iron. For comparison, also tests with the grey iron have been executed. It was found that the gas atmosphere near the interface depends mainly on the content of a carbonaceous substance in the mould. In the green sand moulds with 5% of seacoal or bonded with furan resin, after the mould filling, a sudden increase in the hydrogen content and the drop of oxygen is observed. This gas evolution results from the oxidation of carbon and reduction of water vapour in the mould material, and also from the reduction of water vapour and alloy reoxidation. In carbon-free sand, the evolution in the gas composition is slower because water vapour is reduced only at the interface. Changes of oxygen and hydrogen content in the controlled zone are determined by the transport phenomena

Effect of atmosphere in a foundry mould on casting surface quality

Changes of gas pressure in the moulding sand in the zone adjacent to mould cavity were analysed during pouring of cast iron. No significant effect of pressure on the surface quality of castings was observed. In the second series of tests, the concentration of hydrogen in the gas atmosphere was measured. It has been found that the value of this concentration depends on metal composition and is particularly high in cast iron containing magnesium. This is due to the reduction of water vapour with the element that has high affinity to oxygen. The presence of hydrogen causes the formation of gas-induced defects on the casting surface