D3DXIntersectTri

Computes the intersection of a ray and a triangle.

BOOL D3DXIntersectTri(
  CONST D3DXVECTOR3 * p0,
  CONST D3DXVECTOR3 * p1,
  CONST D3DXVECTOR3 * p2,
  CONST D3DXVECTOR3 * pRayPos,
  CONST D3DXVECTOR3 * pRayDir,
  FLOAT * pU,
  FLOAT * pV,
  FLOAT * pDist
);

Parameters

p0

[in] Pointer to a D3DXVECTOR3 structure, describing the first triangle vertex position.

p1

[in] Pointer to a D3DXVECTOR3 structure, describing the second triangle vertex position.

p2

[in] Pointer to a D3DXVECTOR3 structure, describing the third triangle vertex position.

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.

pU

[out] Barycentric hit coordinates, U.

pV

[out] Barycentric hit coordinates, V.

pDist

[out] Ray-intersection parameter distance.

Return Values

Returns TRUE if the ray intersects the area of the triangle. Otherwise, returns FALSE.

Remarks

The D3DXIntersect 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.