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Fix for b2PolygonShape::ComputeDistance #124

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Fix for b2PolygonShape::ComputeDistance #124

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45 changes: 19 additions & 26 deletions liquidfun/Box2D/Box2D/Collision/Shapes/b2PolygonShape.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -262,43 +262,36 @@ void b2PolygonShape::ComputeDistance(const b2Transform& xf, const b2Vec2& p, flo
B2_NOT_USED(childIndex);

b2Vec2 pLocal = b2MulT(xf.q, p - xf.p);
float32 maxDistance = -FLT_MAX;
b2Vec2 normalForMaxDistance = pLocal;

for (int32 i = 0; i < m_count; ++i)
{
float32 dot = b2Dot(m_normals[i], pLocal - m_vertices[i]);
if (dot > maxDistance)
const b2Vec2& p0 = m_vertices[i - 1 >= 0 ? i - 1 : m_count - 1];
const b2Vec2& p1 = m_vertices[i];
const b2Vec2& p2 = m_vertices[i + 1 < m_count ? i + 1 : 0];
b2Vec2 dist = pLocal - p1;
if (b2Dot(dist, p1 - p0) > 0.0f && b2Dot(dist, p1 - p2) > 0.0f)
{
maxDistance = dot;
normalForMaxDistance = m_normals[i];
*distance = dist.Length();
*normal = b2Mul(xf.q, dist);
if (*distance > 0.0f)
*normal /= *distance;
return;
}
}

if (maxDistance > 0)
float32 maxDistance = -FLT_MAX;
b2Vec2 normalForMaxDistance = pLocal;
for (int32 i = 0; i < m_count; ++i)
{
b2Vec2 minDistance = normalForMaxDistance;
float32 minDistance2 = maxDistance * maxDistance;
for (int32 i = 0; i < m_count; ++i)
float32 dot = b2Dot(m_normals[i], pLocal - m_vertices[i]);
if (dot > maxDistance)
{
b2Vec2 distance = pLocal - m_vertices[i];
float32 distance2 = distance.LengthSquared();
if (minDistance2 > distance2)
{
minDistance = distance;
minDistance2 = distance2;
}
maxDistance = dot;
normalForMaxDistance = m_normals[i];
}

*distance = b2Sqrt(minDistance2);
*normal = b2Mul(xf.q, minDistance);
normal->Normalize();
}
else
{
*distance = maxDistance;
*normal = b2Mul(xf.q, normalForMaxDistance);
}
*distance = maxDistance;
*normal = b2Mul(xf.q, normalForMaxDistance);
}

bool b2PolygonShape::RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
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