bool b2EdgeShape::RayCast()

in Box2D/Collision/Shapes/b2EdgeShape.cpp [55:115]

• 46 lines of code
• 8 McCabe index (conditional complexity)

bool b2EdgeShape::RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
							const b2Transform& xf, int32 childIndex) const
{
	B2_NOT_USED(childIndex);

	// Put the ray into the edge's frame of reference.
	b2Vec2 p1 = b2MulT(xf.q, input.p1 - xf.p);
	b2Vec2 p2 = b2MulT(xf.q, input.p2 - xf.p);
	b2Vec2 d = p2 - p1;

	b2Vec2 v1 = m_vertex1;
	b2Vec2 v2 = m_vertex2;
	b2Vec2 e = v2 - v1;
	b2Vec2 normal(e.y, -e.x);
	normal.Normalize();

	// q = p1 + t * d
	// dot(normal, q - v1) = 0
	// dot(normal, p1 - v1) + t * dot(normal, d) = 0
	float32 numerator = b2Dot(normal, v1 - p1);
	float32 denominator = b2Dot(normal, d);

	if (denominator == 0.0f)
	{
		return false;
	}

	float32 t = numerator / denominator;
	if (t < 0.0f || input.maxFraction < t)
	{
		return false;
	}

	b2Vec2 q = p1 + t * d;

	// q = v1 + s * r
	// s = dot(q - v1, r) / dot(r, r)
	b2Vec2 r = v2 - v1;
	float32 rr = b2Dot(r, r);
	if (rr == 0.0f)
	{
		return false;
	}

	float32 s = b2Dot(q - v1, r) / rr;
	if (s < 0.0f || 1.0f < s)
	{
		return false;
	}

	output->fraction = t;
	if (numerator > 0.0f)
	{
		output->normal = -normal;
	}
	else
	{
		output->normal = normal;
	}
	return true;
}