Fig 9. Linking density volume parameters to characteristics of human vision.

Here, d is the fixed distance from the participant to the screen (in our case 65cm), while h that we use as the kernel size for the density volume (see Fig 5), depends on the view angle β (or rather, on one half of this angle, β /2). β is set to 2° for foveal interaction to 5° for parafoveal interaction.