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| // The intersection of two lines is a solution to P0 + s0*D0 = P1 + s1*D1.
// Rewrite this as s0*D0 - s1*D1 = P1 - P0 = Q. If DotPerp(D0, D1)) = 0,
// the lines are parallel. Additionally, if DotPerp(Q, D1)) = 0, the
// lines are the same. If Dotperp(D0, D1)) is not zero, then
// s0 = DotPerp(Q, D1))/DotPerp(D0, D1))
// produces the point of intersection. Also,
// s1 = DotPerp(Q, D0))/DotPerp(D0, D1))
Vector2<Real> diff = line1.origin - line0.origin;
Real D0DotPerpD1 = DotPerp(line0.direction, line1.direction);
if (D0DotPerpD1 != (Real)0)
{
// The lines are not parallel.
result.intersect = true;
result.numIntersections = 1;
Real invD0DotPerpD1 = ((Real)1) / D0DotPerpD1;
Real diffDotPerpD0 = DotPerp(diff, line0.direction);
Real diffDotPerpD1 = DotPerp(diff, line1.direction);
Real s0 = diffDotPerpD1*invD0DotPerpD1;
Real s1 = diffDotPerpD0*invD0DotPerpD1;
result.line0Parameter[0] = s0;
result.line1Parameter[0] = s1;
result.point = line0.origin + s0 * line0.direction;
}
else
{
// The lines are parallel.
Normalize(diff);
Real diffNDotPerpD1 = DotPerp(diff, line1.direction);
if (std::abs(diffNDotPerpD1) != (Real)0)
{
// The lines are parallel but distinct.
result.intersect = false;
result.numIntersections = 0;
}
else
{
// The lines are the same.
result.intersect = true;
result.numIntersections = std::numeric_limits<int>::max();
Real maxReal = std::numeric_limits<Real>::max();
result.line0Parameter[0] = -maxReal;
result.line0Parameter[1] = +maxReal;
result.line1Parameter[0] = -maxReal;
result.line1Parameter[1] = +maxReal;
}
} |
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