//////////////////////////////////////////////////////////////////////////
// buildTangents
void MdlMesh::buildTangents()
{
BcVec3d* pTan1 = new BcVec3d[ aVertices_.size() * 2 ];
BcVec3d* pTan2 = pTan1 + aVertices_.size();
memset( pTan1, 0, sizeof( BcVec3d ) * aVertices_.size() * 2 );
for ( BcU32 i = 0; i < ( aIndices_.size() / 3 ); ++i )
{
BcU32 TA = aIndices_[ ( i * 3 ) + 0 ].iVertex_;
BcU32 TB = aIndices_[ ( i * 3 ) + 1 ].iVertex_;
BcU32 TC = aIndices_[ ( i * 3 ) + 2 ].iVertex_;
MdlVertex& VertA = aVertices_[ TA ];
MdlVertex& VertB = aVertices_[ TB ];
MdlVertex& VertC = aVertices_[ TC ];
BcVec3d VertPosA = VertA.Position_;
BcVec3d VertPosB = VertB.Position_;
BcVec3d VertPosC = VertC.Position_;
BcVec2d VertUVA = VertA.UV_;
BcVec2d VertUVB = VertB.UV_;
BcVec2d VertUVC = VertC.UV_;
BcReal X1 = VertPosB.x() - VertPosA.x();
BcReal X2 = VertPosC.x() - VertPosA.x();
BcReal Y1 = VertPosB.y() - VertPosA.y();
BcReal Y2 = VertPosC.y() - VertPosA.y();
BcReal Z1 = VertPosB.z() - VertPosA.z();
BcReal Z2 = VertPosC.z() - VertPosA.z();
BcReal S1 = VertUVB.x() - VertUVA.x();
BcReal S2 = VertUVC.x() - VertUVA.x();
BcReal T1 = VertUVB.y() - VertUVA.y();
BcReal T2 = VertUVC.y() - VertUVA.y();
BcReal InvR = ( S1 * T2 - S2 * T1 );
BcReal R = 1.0f / InvR;
// Validation so it doesn't break everything, just set to a dummy value.
if( BcAbs( InvR ) < 1e6f )
{
R = 0.0f;
}
BcVec3d SDir( ( T2 * X1 - T1 * X2 ) * R, ( T2 * Y1 - T1 * Y2 ) * R, ( T2 * Z1 - T1 * Z2 ) * R );
BcVec3d TDir( ( S1 * X2 - S2 * X1 ) * R, ( S1 * Y2 - S2 * Y1 ) * R, ( S1 * Z2 - S2 * Z1 ) * R );
pTan1[ TA ] += SDir;
pTan1[ TB ] += SDir;
pTan1[ TC ] += SDir;
pTan2[ TA ] += TDir;
pTan2[ TB ] += TDir;
pTan2[ TC ] += TDir;
}
for ( BcU32 i = 0; i < aVertices_.size(); ++i )
{
MdlVertex& Vert = aVertices_[ i ];
BcVec3d Tangent;
const BcVec3d N = Vert.Normal_;
const BcVec3d& T = pTan1[ i ];
Tangent = ( T - N * N.dot( T ) );
Tangent.normalise();
// Calculate handedness
BcReal W = ( N.cross( T ).dot( pTan2[ i ] ) < 0.0f ) ? -1.0f : 1.0f;
if ( W < 0.0f )
{
Tangent = -Tangent;
}
Vert.bTangent_ = BcTrue;
Vert.Tangent_ = Tangent;
// Validate, and create a dummy value.
BcReal Mag = Tangent.magnitude();
if( BcAbs( Mag - 1.0f ) > 0.0001f )
{
Vert.Tangent_.set( 0.0f, 0.0f, 0.0f );
}
}
delete[] pTan1;
}
