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LPD3DXMESH Collision Detection

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I''ve written this function in order to determine if a line segment has passed into or through a mesh. For some reason it is only returning true if pVStartPoint is trapped inside a mesh and pVEndPoint is outside the mesh.
bool CEGIMesh::Collide( D3DXVECTOR3 *pVStartPoint, D3DXVECTOR3 *pVEndPoint )
	D3DXVECTOR3 Direction;
	float DistTraveled;
	D3DXVec3Subtract( &Direction, pVStartPoint, pVEndPoint );	
	DistTraveled = D3DXVec3Length( &Direction );
	if ( DistTraveled == 0 ) return false;

	BOOL Hit;
	DWORD FaceIndex1, FaceIndex2;
	float U, V, DistToCollision;
	DWORD nHits1, nHits2;
	r = D3DXIntersect( m_pMesh, pVStartPoint, &Direction, &Hit, &FaceIndex1, &U, &V, &DistToCollision, &pAllHits, &nHits1 );

	if ( !Hit ) return false;

	r = D3DXIntersect( m_pMesh, pVEndPoint, &Direction, &Hit, &FaceIndex2, &U, &V, &DistToCollision, &pAllHits, &nHits2 );	
	if ( nHits1 != nHits2 ) return true;
return false;
The function checks if a ray from pVStartPoint passes through as many faces as a ray from pVEndPoint. If not than a face lies directly between them. If anyone could help I''d be very grateful. Thanks in advance

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Guest Anonymous Poster
wouldn''t Direction need to be -Direction in one of the D3DXIntersect calls?

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Its amazing how a good night''s rest can help find the problem. In a matter of minutes this morning I found the answer.

Your right. Direction is backwards, but in both the D3DXIntersect calls.

D3DXVec3Subtract( &Direction, pVStartPoint, pVEndPoint );
should be
D3DXVec3Subtract( &Direction, pVEndPoint, pVStartPoint );

Thanks for your help.

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