D3DXIntersectSubset function

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

Syntax

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

Parameters

pMesh [in]

Type: LPD3DXBASEMESH

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

AttribId [in]

Type: DWORD

Attribute identifier of the subset to intersect with.

pRayPos [in]

Type: const D3DXVECTOR3*

Pointer to a D3DXVECTOR3 structure, specifying the point where the ray begins.

pRayDir [in]

Type: const D3DXVECTOR3*

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

pHit [out]

Type: BOOL*

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]

Type: DWORD*

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

pU [out]

Type: FLOAT*

Pointer to a barycentric hit coordinate, U.

pV [out]

Type: FLOAT*

Pointer to a barycentric hit coordinate, V.

pDist [out]

Type: FLOAT*

Pointer to a ray intersection parameter distance.

ppAllHits [out]

Type: LPD3DXBUFFER*

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

pCountOfHits [out]

Type: DWORD*

Number of elements in the array returned from ppAllHits.

Return value

Type: HRESULT

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

See also

Mesh Functions