Board coordinate system

The Board is NodeKit's name for the region of the Agent's display where visual content is rendered. Locations on the Board are described using Board coordinates, where:

• (0, 0) is the center of the Agent's display.
• Positive increases in the first coordinate (x) causes movement in the rightward direction.
• Positive increases in the second coordinate (y) causes movement in the upward direction.
• Units are normatively specified as reference pixels. A reference pixel is a unit of visual angle defined in the W3C specification as the visual angle of one pixel on a device with 96 dpi at an arm's length. Given an arm's length of 28 inches, a reference pixel is ~0.0213° of visual angle. In practice, NodeKit interprets Board units as CSS pixels, which the W3C spec recommends be mapped by the browser 1:1 with reference pixels. Note that this mapping is always approximate, in that the browser 1) does not know the Agent's viewing position, and 2) does not know the physical size of device pixels.

Thus, a Board coordinate of (100, 100) would indicate a point that is 100 pixels to the right, and 100 pixels up from the Agent's display.

Long story short: the NodeKit Board is the central 1024 x 768 pixel region on the agent's display.

Size of Board in visual degrees

The size of the normative Board (1024 x 768 reference pixels) is ~21.81° x 16.35° of the Agent's visual field when viewed straight on.