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 point where the ray begins.

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 the following value: 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, the value of [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 represents a change in coordinate systems. What holds true for Cartesian coordinates holds true for barycentric coordinates.

Barycentric coordinates define a point inside a triangle in terms of the triangle's vertices. For a more in-depth description of barycentric coordinates, see Mathworld's Barycentric Coordinates Description.

Requirements

Header: Declared in D3dx9mesh.h.