D3DXIntersectSubset

Intersects the specified ray with the given mesh subset. This provides similar functionality to D3DXIntersect.

HRESULT D3DXIntersectSubset(
  LPD3DXBASEMESH     pMesh,
  DWORD              AttribId,  
  CONST D3DXVECTOR3* pRayPos,
  CONST D3DXVECTOR3* pRayDir,
  BOOL*              pHit,
  DWORD*             pFaceIndex,
  FLOAT*             pU,
  FLOAT*             pV,
  FLOAT*             pDist,
  LPD3DXBUFFER*      ppAllHits,
  DWORD*             pCountOfHits
);

Parameters

pMesh

[in] Pointer to an ID3DXBaseMesh interface, representing the mesh to be tested. The mesh must be attribute sorted.

AttribId

[in] Attribute identifier of the subset to intersect with.

pRayPos

[in] Pointer to a D3DXVECTOR3 structure, specifying the origin coordinate of the ray.

pRayDir

[in] Pointer to a D3DXVECTOR3 structure, specifying the direction of the ray.

pHit

[out] Pointer to a BOOL. If the ray intersects a triangular face on the mesh, this value will be set to TRUE. Otherwise, this value is set to FALSE.

pFaceIndex

[out] Pointer to an index value of the face closest to the ray origin, if pHit is TRUE.

pU

[out] Pointer to a barycentric hit coordinate, U.

pV

[out] Pointer to a barycentric hit coordinate, V.

pDist

[out] Pointer to a ray intersection parameter distance.

ppAllHits

[out] Array of D3DXINTERSECTINFO structures, representing all hits, not just closest hits.

pCountOfHits

[out] Number of elements in the array returned from ppAllHits.

Return Values

If the function succeeds, the return value is D3D_OK.

If the function fails, the return value can be E_OUTOFMEMORY.

Remarks

The D3DXIntersectSubset function provides a way to understand points in and around a triangle, independent of where the triangle is actually located. This function returns the resulting point by using the following equation: V1 + U(V2-V1) + V(V3-V1).

Any point in the plane V1V2V3 can be represented by the barycentric coordinate (U,V). The parameter U controls how much V2 gets weighted into the result and the parameter V controls how much V3 gets weighted into the result. Lastly, 1-U-V controls how much V1 gets weighted into the result.

Barycentric coordinates are a form of general coordinates. In this context, using barycentric coordinates simply represents a change in coordinate systems. What holds true for Cartesian coordinates holds true for barycentric coordinates.

Requirements

  Header: Declared in D3dx8mesh.h.
  Import Library: Use D3dx8.lib.