## File: intersect.cmd

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evolver 2.70+ds-4
 `12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364` ``````// intersect.cmd // Evolver command to detect intersection of linear edges and facets. // For each facet, finds if any edge intersects in interior. // Usage: read "intersect.cmd" // detect // Output: prints ids of facets and edges that intersect. // Notes: In quadratic model, treats edges and facets as simply linear. // Will not work in Lagrange model. intersect_eps := 1e-10 // tolerance for being equal to zero detect := { local ax,ay,az,bx,by,bz,cx,cy,cz,acx,bcx,px,py,pz,qx,qy,qz,qpx,qcx; local denom,lambda,mu,sigma; local acy,acz,bcy,bcz,qpy,qpz,qcy,qcz; if lagrange then { printf "intersect.cmd will not work in Lagrange model.\n";return;}; foreach facet ff do { ax := ff.vertex[1].x; ay := ff.vertex[1].y; az := ff.vertex[1].z; bx := ff.vertex[2].x; by := ff.vertex[2].y; bz := ff.vertex[2].z; cx := ff.vertex[3].x; cy := ff.vertex[3].y; cz := ff.vertex[3].z; acx := ax-cx; acy := ay-cy; acz := az- cz; bcx := bx-cx; bcy := by-cy; bcz := bz- cz; foreach edge ee do { px := ee.vertex[1].x; py := ee.vertex[1].y; pz := ee.vertex[1].z; qx := ee.vertex[2].x; qy := ee.vertex[2].y; qz := ee.vertex[2].z; qpx := qx-px; qpy := qy-py; qpz := qz-pz; qcx := qx-cx; qcy := qy-cy; qcz := qz-cz; denom := qpx*(acy*bcz-acz*bcy) - qpy*(acx*bcz-acz*bcx) + qpz*(acx*bcy-acy*bcx); if ( abs(denom) < intersect_eps ) then continue; lambda := (qpx*(qcy*bcz-qcz*bcy) - qpy*(qcx*bcz-qcz*bcx) + qpz*(qcx*bcy-qcy*bcx))/denom; if ( lambda <= intersect_eps ) then continue; mu := (qpx*(acy*qcz-acz*qcy) - qpy*(acx*qcz-acz*qcx) + qpz*(acx*qcy-acy*qcx))/denom; if ( mu <= intersect_eps ) then continue; if ( lambda + mu > 1-intersect_eps ) then continue; sigma := (qcx*(acy*bcz-acz*bcy) - qcy*(acx*bcz-acz*bcx) + qcz*(acx*bcy-acy*bcx))/denom; if ( (sigma <= intersect_eps) or (sigma > 1-intersect_eps) ) then continue; // now have intersection printf "Facet %g and edge %g intersect.\n",ff.id,ee.id; } } } // End intersect.cmd // Usage: detect ``````