Material construction/manipulation functions

make-material

Construct a material from a BSDF

make-rgb

Construct a spectrum representing the given RGB values

make-spectrum

Directly construct a spectrum

make-surf

Construct a BSDF of the given type + parameters

make-emittance

Construct an emission function of the given type + parameters

load-texture2d

Load a 2D texture from a file (currently only TGA files supported)