ThermoAnalytics software determines the radiation relationships from each element (or patch) to every other element (or patch) in the model and to the environment (bounding box or natural sky dome, terrain, and sun). To illustrate how the view factors are determined, consider two parallel plates in a simple bounding box environment. The bounding box "offsets" from the geometry do not need to be equal on all sides, so in this example the plates are not centered in the bounding box.
A hemisphere is constructed at the centroid of each side of a planar element. The planar centroid location is not affected by the part thickness (input on the Editor Tab). From this point, rays are cast outward into model space, and intersections with other elements are determined and tabulated. The image below shows a single ray being cast into space and intersecting another element, highlighted in green.
Thousands of rays are cast from each element centroid to determine the view factor to all other elements that are visible from the element centroid. The number of rays that intersect another element determines relative view factor relationship.
