D3DXVec3BaryCentric

Returns a point in Barycentric coordinates, using the specified 3-D vectors.

D3DXVec3BaryCentric( _ 
    VOut As D3DVECTOR, _ 
    V1 As D3DVECTOR, _ 
    V2 As D3DVECTOR, _ 
    V3 As D3DVECTOR, _ 
    f As Single, _ 
    g As Single)

Parameters

VOut

D3DVECTOR type that is the result of the operation, a vector in Barycentric coordinates.

V1

A source D3DVECTOR type.

V2

A source D3DVECTOR type.

V3

A source D3DVECTOR type.

f

Weighting factor. See Remarks.

g

Weighting factor. See Remarks.

Error Codes

If the function fails, an error is raised and Err.Number can be set to one of the following values.

For information on trapping errors, see the Microsoft® Visual Basic® Error Handling topic.

Remarks

The D3DXVec3BaryCentric 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 + f(V2-V1) + g(V3-V1).

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

Note the following relations.

• If (f>=0 And g>=0 And 1-f-g>=0), the point is inside the triangle V1V2V3.
• If (f==0 And g>=0 And 1-f-g>=0), the point is on the line V1V3.
• If (f>=0 And g==0 And 1-f-g>=0), the point is on the line V1V2.
• If (f>=0 And g>=0 And 1-f-g==0), the point is on the line V2V3.

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.