dFdxLinear

Compute the first-order derivative of a linear two-dimensional function <i>f</i> with respect to X and store the result in <code>dest</code>. <p> This method computes the constant rate of change for <i>f</i> given the three values of <i>f</i> at the specified three inputs <code>(v0X, v0Y)</code>, <code>(v1X, v1Y)</code> and <code>(v2X, v2Y)</code>.

@param v0X the x coordinate of the first triangle vertex @param v0Y the y coordinate of the first triangle vertex @param f0X the x component of the value of <i>f</i> at the first vertex @param f0Y the y component of the value of <i>f</i> at the first vertex @param v1X the x coordinate of the second triangle vertex @param v1Y the y coordinate of the second triangle vertex @param f1X the x component of the value of <i>f</i> at the second vertex @param f1Y the y component of the value of <i>f</i> at the second vertex @param v2X the x coordinate of the third triangle vertex @param v2Y the y coordinate of the third triangle vertex @param f2X the x component of the value of <i>f</i> at the third vertex @param f2Y the y component of the value of <i>f</i> at the third vertex @param dest will hold the result @return dest