area VEX function

Returns the area of the micropolygon containing a variable such as P.

Contexts: cop, displace, fog, light, photon, shadow, surface

See also: volume, Du, Dv

  1. float area(vector p)

This is a more accurate and convenient method to get the micropolygon area than multiplying the length of Du(P) by the length of Dv(P). This function is typically used to get the shading area in pixels.

Note

This function works because VEX “knows” that the variable P has derivatives (dPdu and dPdv). Passing a literal vector instead of a special variables such as P will return 0 since VEX will not be able to access the derivatives.

You can specify optional parameters to control the computation. The optional parameter "extrapolate" controls whether to do derivative extrapolation at the edges.

Examples

Return the area of the current micro-polygon in camera space:

area(P)

Return the area of the current micro-polygon in NDC space:

area(transform("ndc", P))

Returns 0, since the argument is not a variable VEX knows the derivatives for:

area({0.1, 2.3, 4.5})