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Lecture 14: Material Modeling (12)

What kind of function is used to represent the BRDF of a glossy material? Are they generally modeled using the microfacet model? Or do other functions exist for modeling smooth, glossy materials?


I wonder if we could achieve the same effect without using a BRDF with a naive raytracing procedure by defining our 3D mesh to have these surface bumps and noise, causing the surface normals to point in various directions. Does anyone else think this should still produce a similar effect?


@ryanpmeyer, I imagine that would probably have a similar effect, but it would require you to have a much higher polygon mesh. If you look at the teacup example from a few slides ago, you will see that the mesh is not nearly fine enough to model bumps such as this. I believe the benefit of BRDF is that it allows us to generate a variety of materials on the same, relatively low resolution mesh.


@ryanpmeyer, like @sean-dooher said you could do that, but it would make the mesh file so huge no modern computer could reasonably process it. A way to add surface details to a mesh is to use a normal map - an image whose r,g,b values correspond to the desired x,y,z coordinates of the mesh's surface normals. This can be mapped onto a mesh to get interesting surface effects, like roughness on a small scale, or large bumps / warping on a larger scale. It's what is used in most 3D applications to "fake" surface details without increasing a mesh's polygon count. Just google "<material name> normal map" and you can see all sorts of interesting examples!

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