It is necessary that interface elements do not are covered by fingers, hands or arms during the interaction.
The partial occlusion of the screen caused by fingers, hands and arms when users interacting with surface are an aspect that should be into account in the design of a multi-touch interface. So, the design of interface should avoid occlusions that affecting the interaction, and the hand and arm movements should be considered in the placing the elements in the user interface, in order to prevent early muscle fatigue.
Examples of finger occluding pie menu.
Challenges for Designing the User Experience of Multi-touch Interfaces, 2010
Challenge, Interface, Interaction, Layout, Motor, Multi-touch, Overlap.
Avoid ﬁne motor input, the interface should allow whole-handed and multi-ﬁnger input.
The interface capability to enable whole-handed and multi-finger input is a relevant feature. This feature is appreciated by users with hand tremors or arthritis.
A participant using whole hand.
Illustration adapted from Exploring the Accessibility and Appeal of Surface Computing for Older Adult Health Care Support
Exploring the Accessibility and Appeal of Surface Computing for Older Adult Health Care Support,2010
Accessibility, Adaptability, Elderly, Interaction, Interface, Layout, Multi-Touch.