Issue I223 [70,medium,resolved] Improvements in clipping line to rectangle. Clipping is used for things like detecting if a particle trajectory crosses a PA grid cell, splatting the particle if cell is an electrode. Problem known to affect versions prior to 8.0-beta12h: Particles may skip through PA at el=180deg due to numerical error in clipping. Problem seems to tend to occur when a particle is flying at an angle of elevation=180degrees. Changing elevation to 179.9999999... eliminates the effect. Problems occurs on some compilers and initally seemed related to the floating point code in matrix.cpp rt/el/az_matrix, but it it not so clear anymore since this may just be a side-effect. See theo/20060919 examples. Affects 7.0.1 and above and 8.0betas. Also affects 7.0.0 but to a somewhat lesser extent. Update 8.0-beta12h (2006-09-20): SIMION now treats nearly horizontal lines (i.e. 1/|slope| > 1e15) specially. This issue is probably resolved now. Update: 8.0.6-TEST10 makes some further minor robustness improvements to 2D clip detection--e.g. treating X and Y exactly symmetrically. Update: 18.104.22.168/22.214.171.124 - made similar clip detection improvements in 3D. See also Issue I588.