Method intersectionPoints

src/IECoreScene/SpherePrimitiveEvaluator.cpp:371–437

Implementation derived from Wild Magic (Version 2) Software Library, available from http://www.geometrictools.com/Downloads/WildMagic2p5.zip under free license

/// Implementation derived from Wild Magic (Version 2) Software Library, available
/// from http://www.geometrictools.com/Downloads/WildMagic2p5.zip under free license
int SpherePrimitiveEvaluator::intersectionPoints( const Imath::V3f &origin, const Imath::V3f &direction,
	std::vector<PrimitiveEvaluator::ResultPtr> &results, float maxDistance ) const
{
	results.clear();

	Imath::V3f dir = direction.normalized();
	(void)direction;
	float a0 = origin.dot(origin) - m_sphere->radius() * m_sphere->radius();
	float a1 = dir.dot( origin );
	float discr = a1 * a1 - a0;

	if (discr < 0.0)
	{
		return 0;
	}

	if ( discr >= std::numeric_limits<float>::epsilon() )
	{
		float root = sqrt( discr );
		float t0 = -a1 - root;

		if ( t0 >= 0.0 )
		{
			Imath::V3f p0 = origin + t0 * dir;
			if ( (origin - p0).length() < maxDistance )
			{
				ResultPtr r = boost::static_pointer_cast< Result > ( createResult() );
				r->m_p = p0;

				results.push_back( r );
			}
		}

		float t1 = -a1 + root;
		if ( t1 >= 0.0 )
		{
			Imath::V3f p1 = origin + t1 * dir;
			if ( (origin - p1).length() < maxDistance )
			{
				ResultPtr r = boost::static_pointer_cast< Result > ( createResult() );
				r->m_p = p1;

				results.push_back( r );
			}
		}
	}
	else
	{
		float t = -a1;

		if ( t >= 0.0 )
		{
			Imath::V3f p = origin + t * dir;
			if ( (origin - p).length() < maxDistance )
			{
				ResultPtr r = boost::static_pointer_cast< Result > ( createResult() );
				r->m_p = p;