I wrote a ray tracer that implements various BRDF models (Oren Nayar, Lamber, Torrance Sparrow and so on). Now I'm trying to implement a BRDF from measured data.I choose the Cornell database data available here:http://www.graphics.cornell.edu/online/measurements/reflectance/spraypaints/index.htmlI want to use them because there's a representation of the data as spectrum with 31 sample (my ray tracer use spectral data for light calculation and then convert them to CIE XYZ and then RGB values for the final image rendering).Which is the correct way to use this data?Which sample technique must be used? Why phi_out has all negative value?Can I calculate phi_out using the same approximation as the one I used in Oren Nayar, so ||View - Normal * (View.dot(normal)||
Ray tracing - BRDF using Cornell measured spectral data
raytracing;brdf