In the Engineering Reference from energy plus we can get information about Surface Geometry:
5.4.3 Surface Geometry Shadow calculations first require that the building surfaces be described geometrically. Surfaces are described by the coordinates of their vertices in a three dimensional Cartesian coordinate system. This Right-hand coordinate system has the X-axis pointing east, the Y-axis pointing north, and the Z-axis pointing up (see figure below). The azimuth angle ( ) of a surface is the angle from the north axis to the projection onto the X-Y plane of a normal to the surface (clockwise positive). The surface tilt angle (ϕ) is the angle between the Z-axis and the normal to the surface. The vertices are recorded in counter-clockwise sequence (as the surface is viewed from outside its zone). During surface entry, surfaces are checked for convex or non-convex shape. If non-convex and inappropriate (used as a receiving surface) then a severe error is produced telling the user that shadowing calculations may be inaccurate. Similarly collinear points (or as noted below, points within 1 mm distance) are removed unless removing would make an illegal surface (less than 3 points). But degenerate collinear surfaces should be removed – they make the shadowing routines do extra work which takes extra time. Collinear – points that essentially form a “line” rather than a surface shape. Resolution of 1mm or less – near collinear points. Note that the resolution on surfaces/shadowing is 1 mm – using resolution beyond that will result in truncation of the shadowing.
I have surface with dimension of 2 m x 0.009 m (9 mm). When I run the simulation I got this warning:
* Warning * GetVertices: Distance between two vertices < .01, possibly coincident. for Surface=ZONE_4_SRF_1, in Zone=ZONE_4
* ~~~ * Vertex [2]=(-1.00,-2.00,0.00)
* ~~~ * Vertex [1]=(-1.00,-2.00,9.00E-003)
* ~~~ * Dropping Vertex [2].
* Warning * GetVertices: Distance between two vertices < .01, possibly coincident. for Surface=ZONE_4_SRF_1, in Zone=ZONE_4
* ~~~ * Vertex [3]=(1.00,-2.00,9.00E-003)
* ~~~ * Vertex [2]=(1.00,-2.00,0.00)
* ~~~ * Cannot Drop Vertex [3]; Number of Surface Sides at minimum. This surface is now a degenerate surface. . . . So, Is it possible to change the setting of minimum distance to avoid collinear points ?
When I read the reference I thought the minimum surface is 1 mm because it will be collinear points if less than that distance, but it already became collinear points because Distance between two vertices < .01 (10 mm). Or 10 mm is the minimum surface in Energy Plus model?
Thank you very much.
