Documentation for Users
1.0.2
Perception Toolbox for Virtual Reality (PTVR) Manual

The 3D perimetric coordinate system belongs to the class of spherical coordinate systems. The 3D perimetric coordinate system is used extensively by vision scientists.
In this coordinate system, the 3D position of a point P is defined by the 3 following coordinates:
– Halfmeridian (from 0° to 360°). The Halfmeridian of Point P in the figures below is 135°.
– Eccentricity (from 0° to 180°). the Eccentricity of Point P in the figures below is 20°.
– Radial Distance (in meters) – corresponds to the radius of the sphere on which P is lying (i.e. constant distance between Origin and P).
 
Figure 1: Static representation of the 3D perimetric coordinate system.  Figure 2: Animation (horizontal rotation about the Y axis) of figure 1 to allow you to build a better mental representation of the 3D structure of the figure (as if you were able to look at the static coordinate system from different angles). 
 
Figure 3: Eccentricity of point P varies from 8° to 40° while keeping Halfmeridian constant at 135°.  Figure 4: Halfmeridian of point P varies from 0° to 360° while keeping eccentricity constant at 20°. 
Howard, I. P., & Rogers, B. J. (2008). chap. 20. Classification of binocular disparity. In Seeing in Depth (Vol. 2). Oxford University Press. https://oxford.universitypressscholarship.com/view/10.1093/acprof:oso/9780195367607.001.0001/acprof9780195367607chapter20
Wikipedia contributors. (2022, February 16). Spherical coordinate system. In Wikipedia, The Free Encyclopedia. Retrieved 15:18, February 21, 2022, from https://en.wikipedia.org/w/index.php?title=Spherical_coordinate_system&oldid=1072122604