int ON_Intersect( const ON_Plane& plane, const ON_Circle& circle, ON_3dPoint& point0, ON_3dPoint& point1 ) { int rval = -1; ON_Line xline; double a,b; bool rc = ON_Intersect(plane, circle.Plane(), xline); if(rc) { rval = ON_Intersect(xline, circle, &a, point0, &b, point1); } else { double d = plane.plane_equation.ValueAt( circle.Center() ); if(d<ON_ZERO_TOLERANCE) rval =3; else rval = 0; } return rval; }
int ON_Intersect( const ON_Line& line, const ON_Circle& circle, double* line_t0, ON_3dPoint& circle_point0, double* line_t1, ON_3dPoint& circle_point1 ) { // transform to coordinate system where equation of circle // is x^2 + y^2 = R^2 and solve for line parameter(s). ON_Xform xform; xform.ChangeBasis( circle.plane, ON_xy_plane ); xform.ChangeBasis( ON_xy_plane, circle.plane ); ON_Line L = line; L.Transform(xform); double r = fabs(circle.radius); double tol = r*ON_SQRT_EPSILON; if ( tol < ON_ZERO_TOLERANCE ) tol = ON_ZERO_TOLERANCE; int xcnt; if ( fabs(L.from.x - L.to.x) <= tol && fabs(L.from.y - L.to.y) <= tol && fabs(L.from.z - L.to.z) > tol ) { xcnt = 0; } else { xcnt = Intersect2dLineCircle( L.from, L.to, r, tol, line_t0, line_t1 ); if ( xcnt == 3 ) xcnt = 1; } if ( xcnt == 0 ) { if ( L.ClosestPointTo( circle.Center(), line_t0 ) ) { xcnt = 1; *line_t1 = *line_t0; } } ON_3dPoint line_point1, line_point0 = line.PointAt(*line_t0); circle_point0 = circle.ClosestPointTo(line_point0); double d1, d0 = line_point0.DistanceTo(circle_point0); if ( xcnt == 2 ) { line_point1 = line.PointAt(*line_t1); circle_point1 = circle.ClosestPointTo(line_point1); d1 = line_point1.DistanceTo(circle_point1); } else { line_point1 = line_point0; circle_point1 = circle_point0; d1 = d0; } if ( xcnt==2 && (d0 > tol && d1 > tol) ) { xcnt = 1; if ( d0 <= d1 ) { *line_t1 = *line_t0; line_point1 = line_point0; circle_point1 = circle_point0; d1 = d0; } else { *line_t0 = *line_t1; line_point0 = line_point1; circle_point0 = circle_point1; d0 = d1; } } if ( xcnt == 1 && d0 > tol ) { // TODO: iterate to closest point } return xcnt; }