Im not sure how he did it, but might have been done, but adding a normal map to the floor. So my guess is he used/might have used a program to generate the normal map and then use the bumpmapping effect in C2. I cant see if the normal map is "accurate" or not. So that's why I said he might have used a program to calculate a correct normal map, or maybe just a "fake" one.
However it works like that.
"To calculate the Lambertian (diffuse) lighting of a surface, the unit vector from the shading point to the light source is dotted with the unit vector normal to that surface, and the result is the intensity of the light on that surface. Imagine a polygonal model of a sphere - you can only approximate the shape of the surface. By using a 3-channel bitmap textured across the model, more detailed normal vector information can be encoded. Each channel in the bitmap corresponds to a spatial dimension (X, Y and Z). These spatial dimensions are relative to a constant coordinate system for object-space normal maps, or to a smoothly varying coordinate system (based on the derivatives of position with respect to texture coordinates) in the case of tangent-space normal maps. This adds much more detail to the surface of a model, especially in conjunction with advanced lighting techniques."