shadow VEX function

Calls shadow shaders for the current light source.

Contexts: displace, fog, surface

  1. void shadow(vector Cl&)

  2. void shadow(vector Cl&, vector P, vector L)

Calls shadow shaders for the current light source. This function can only be called from within an illuminance statement. Once the shadows have been computed for a light source, they are fixed for the duration of the shader.