過去的研究已提出在使用者的手、四肢和頭上產生瞬間且強烈的衝擊力回饋來強化虛擬實境的真實感，但在身體上的衝擊力仍鮮少被討論。身體有著很大的表面積，因此可以在多種虛擬實境應用中呈現更多衝擊力型態，例如：在虛擬實境遊戲中身體被受到射擊、爆炸、拳擊、砍擊。我們提出一個原型能夠呈現在身上的多程度多維度之衝擊力陣列。透過獨立控制在3×3陣列的9個彈力衝擊器產生在不同強度、位置和時間順序的空間時間組合。我們做了一個最小可覺差實驗來了解使用者在身體上對衝擊力強度的分辨度。以及時間間隔閾值實驗探討兩個衝擊力刺激之間多少的時間間隔作為分辨連續、同時、分散的衝擊力。基於以上實驗結果，我們製作了虛擬實境實驗來驗證我們的原型產生的衝擊力回饋能夠強化虛擬實境的真實度。

Rendering instant and intense impact feedback on users’ hands, limbs and head to enhance realism in virtual reality (VR) has been proposed in previous works, but impact on body is still less discussed. With a large surface area on body, more impact patterns can be rendered in versatile VR applications, e.g., being shot, blasted, punched or slashed on body in VR games. We propose ImpactVest to render spatio-temporal multilevel impact force feedback on body. By independently controlling nine impactors in a 3×3 layout using elastic force, impact is generated at different levels, positions and time sequences for versatile spatial and temporal combinations. We conducted a just-noticeable difference (JND) study to realize users’ impact level distinguishability on body. A time interval threshold study was then performed to understand what time interval thresholds between two impact stimuli are used to distinguish among simultaneous impact, a continuous impact stroke and two discrete impact stimuli. Base on the results, we conducted a VR experience study to verify that impact feedback from ImpactVest enhances VR realism.

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