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Poly - Line Intersection....almost there...

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McDonut    122
Hey guys, please help me out someone and dont bug me because of my lack of math knowledge. I just cant get polygon line collision to work properly: I''m testing the edges of a triangle against the polys that build up my view frustum. The problem is, when all edges are within the frustum, a collision is still registered. It seems all code i''ve tried so far checks if the endless ray the line describes hits the poly, not the line itself. So I checked with D3DXPlaneIntersectLine() if the edge hits the plane the poly describes, top of the code. And its NOT working! If all lines are inside the frustum the function returns a collision. Is this funtion also only checking the ray against the plane? Well, I''ll post along the code of my current function, I already wasted some nights on this, so please, help me out until I buy my linear algebra book... MLE_API bool mleLineHitsTriangle2(const D3DXVECTOR3& pvLineA, const D3DXVECTOR3& pvLineB, const D3DXVECTOR3& pvTriA, const D3DXVECTOR3& pvTriB, const D3DXVECTOR3& pvTriC, D3DXVECTOR3* pvOut) // =NULL { D3DXVECTOR3 vOut; D3DXPLANE Plane; // die ebene des dreiecks berechnen D3DXPlaneFromPoints(&Plane, &pvTriA, &pvTriB, &pvTriC); // wenn sie die ebene nicht schneidet, kann sie das dreieck nicht schneiden if (D3DXPlaneIntersectLine(&vOut, &Plane, &pvLineA, &pvLineB) == NULL) return false; // der richtungsvektor der linie D3DXVECTOR3 vDir = pvLineB - pvLineA; // Find vectors for two edges sharing vert0 D3DXVECTOR3 edge1 = pvTriB - pvTriA; D3DXVECTOR3 edge2 = pvTriC - pvTriA; // Begin calculating determinant - also used to calculate U parameter D3DXVECTOR3 pvec; D3DXVec3Cross(&pvec, &vDir, &edge2); // If determinant is near zero, ray lies in plane of triangle float det = D3DXVec3Dot(&edge1, &pvec); D3DXVECTOR3 tvec; if(det > 0) { tvec = pvLineA - pvTriA; } else { tvec = pvTriA - pvLineA; det = -det; } if( det < 0.0001f ) return false; // Calculate U parameter and test bounds vOut.x = D3DXVec3Dot(&tvec, &pvec); if(vOut.x < 0.0f || vOut.x > det) return false; // Prepare to test V parameter D3DXVECTOR3 qvec; D3DXVec3Cross(&qvec, &tvec, &edge1); // Calculate V parameter and test bounds vOut.y = D3DXVec3Dot(&vDir, &qvec); if(vOut.y < 0.0f || vOut.x + vOut.y > det) return false; // Calculate t, scale parameters, ray intersects triangle vOut.z = D3DXVec3Dot(&edge2, &qvec); float fInvDet = 1.0f / det; vOut.z *= fInvDet; vOut.x *= fInvDet; vOut.y *= fInvDet; if (pvOut != NULL) *pvOut = vOut; return true; } its got mixed german and english comments cause its mainly taken from the DX ''Pick'' sample

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