The bidirectional reflectance distribution function (BRDF) is a function that defines how incoming light is reflected outward. This web-based visualizer uses the Cook-Torrance model and shows how the material looks on a sphere, and simultaneously displays its evaluated BRDF. Especially the different reflective behavior of specular and diffuse materials are easily visible.
A free, scalable, modern and open source solution for programming lectures supporting auto-testing/grading of programming assignments scaling to thousands of students and several courses.