// Four square roots, not cheap
// Heron's formula
float Triangle::GetArea() const
{
float A = ( m_Vec2 - m_Vec1 ).Length();
float B = ( m_Vec3 - m_Vec2 ).Length();
float C = ( m_Vec1 - m_Vec3 ).Length();
float S = ( A + B + C ) / 2.0f;
return SqRt( S * ( S - A ) * ( S - B ) * ( S - C ) );
}
Vector Quat::GetAxis() const
{
float SinTheta = SqRt( 1.0f - w * w );
if( Abs( SinTheta ) > EPSILON )
{
float Recip = 1.0f / SinTheta;
return Vector( x * Recip, y * Recip, z * Recip );
}
else
{
return Vector();
}
}
bool Cylinder::Intersects( const Segment& s, CollisionInfo* const pInfo /*= NULL*/ ) const
{
Vector d = m_Point2 - m_Point1; // Cylinder axis
Vector m = s.m_Point1 - m_Point1; // Vector from cylinder base to segment base?
Vector n = s.m_Point2 - s.m_Point1; // Segment vector
float md = m.Dot( d );
float nd = n.Dot( d );
float dd = d.Dot( d );
if( md < 0.0f && md + nd < 0.0f )
{
return false;
}
if( md > dd && md + nd > dd )
{
return false;
}
float nn = n.Dot( n );
float mn = m.Dot( n );
float a = dd * nn - nd * nd;
float k = m.Dot( m ) - m_Radius * m_Radius;
float c = dd * k - md * md;
float t = 0.0f;
if( Abs( a ) < SMALLER_EPSILON )
{
// Segment (n) runs parallel to cylinder axis (d)
if( c > 0.0f )
{
return false;
}
if( md < 0.0f )
{
t = -mn / nn;
}
else if( md > dd )
{
t = ( nd - mn ) / nn;
}
else
{
// TODO: This seems to be problematic (or getting here is indicative of an earlier problem)
WARNDESC( "THAT CYLINDER COLLISION BUG" );
t = 0.0f;
}
if( pInfo )
{
Vector Intersection = s.m_Point1 + t * n;
Vector PointOnLine = Line( m_Point1, m_Point2 - m_Point1 ).NearestPointTo( pInfo->m_Intersection );
Vector Normal = ( Intersection - PointOnLine ).GetNormalized();
pInfo->m_Collision = true;
pInfo->m_Intersection = Intersection;
pInfo->m_HitT = t;
pInfo->m_Plane = Plane( Normal, PointOnLine );
}
return true;
}
float b = dd * mn - nd * md;
float Discr = b * b - a * c;
if( Discr < 0.0f )
{
return false;
}
t = ( -b - SqRt( Discr ) ) / a;
if( t < 0.0f || t > 1.0f )
{
return false;
}
// Test endcaps--if we collide with them, count it as not colliding with cylinder
if( md + t * nd < 0.0f )
{
return false;
//// Segment outside cylinder on first side
//if( nd <= 0.0f )
//{
// // Segment pointing away from endcap
// return false;
//}
//float t2 = -md / nd;
//if( k + t2 * ( 2.0f * mn + t2 * nn ) > 0.0f )
//{
// return false;
//}
}
else if( md + t * nd > dd )
{
return false;
//// Segment outside cylinder on second side
//if( nd >= 0.0f )
//{
// // Segment pointing away from endcap
// return false;
//}
//float t2 = ( dd - md ) / nd;
//if( k + dd - 2.0f * md + t2 * ( 2.0f * ( mn - nd ) + t2 * nn ) > 0.0f )
//{
// return false;
//}
}
if( pInfo )
{
Vector Intersection = s.m_Point1 + t * n;
Vector PointOnLine = Line( m_Point1, m_Point2 - m_Point1 ).NearestPointTo( Intersection );
Vector Normal = ( Intersection - PointOnLine ).GetNormalized();
pInfo->m_Collision = true;
pInfo->m_Intersection = Intersection;
pInfo->m_HitT = t;
pInfo->m_Plane = Plane( Normal, PointOnLine );
}
return true;
}
float Quat::Length() const
{
return SqRt( w * w + x * x + y * y + z * z );
}
float Vector4::Length() const
{
return SqRt( ( x * x ) + ( y * y ) + ( z * z ) + ( w * w ) );
}
