dtTriArea2D

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Description

Derives the signed xz-plane area of the triangle ABC, or the relationship of line AB to point C. This section contains detailed documentation for members that don't have a source file. It reduces clutter in the main section of the header.

The vertices are projected onto the xz-plane, so the y-values are ignored.

This is a low cost function than can be used for various purposes. Its main purpose is for point/line relationship testing.

In all cases: A value of zero indicates that all vertices are collinear or represent the same point. (On the xz-plane.)

When used for point/line relationship tests, AB usually represents a line against which the C point is to be tested. In this case:

A positive value indicates that point C is to the left of line AB, looking from A toward B. A negative value indicates that point C is to the right of lineAB, looking from A toward B.

When used for evaluating a triangle:

The absolute value of the return value is two times the area of the triangle when it is projected onto the xz-plane.

A positive return value indicates:

• The vertices are wrapped in the normal Detour wrap direction.
• The triangle's 3D face normal is in the general up direction.

A negative return value indicates:

• The vertices are reverse wrapped. (Wrapped opposite the normal Detour wrap direction.)
• The triangle's 3D face normal is in the general down direction.

dtReal dtTriArea2D  
(  
    const dtReal * a,  
    const dtReal * b,  
    const dtReal * c  
)  
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dtReal dtTriArea2D (     const dtReal * a,     const dtReal * b,     const dtReal * c )

The signed xz-plane area of the triangle.

Parameters