At the topmost level, pointer to 2D contours and their parameters are held by the Mesh Solutions. This relationship is defined in solution.h
The actual set of points are contained within each contour object. Contours are defined in contour.h
When 2D Contours are about to be plotted, a solution value is checked to see if its contours need to be computed. If so they go through the following steps to make a contour.
First the old contours should be deleted and their memory freed. This is not currently done. ( See Things To Do )
The contour is built by calling the function GenerateMeshContour which passes the contour number, the value of the solution along this conoutr and a pointer to the solution to which this contour belongs. (Each 2D solution can have up to ten contours. 1D plots only need 1 contour per solution.)
GenerateMeshContour loops through every element and checks for an intersection of the solution value with that element. It counts the number of elements which intersect it and then allocates room for an appropriate number of contour points. The function which does the intersection calculations is sol_intersect.
Another loop is then made through the elements and this time the points of intersection with the solution value are stored in the Contour Object.
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