A matrix material composed of polymer, preferably of thermoplastic polymer, or coating material. The matrix material includes 0.01 to 50% by weight of an additive for foaming of the matrix material which can be triggered by irradiation with laser light or IR light. The additive includes at least the following constituents: a) at least one absorber material which, embedded or dissolved in the matrix material, absorbs laser light or IR light and brings about local heating in the matrix material at the site of irradiation with laser light or IR light, and b) at least one blowing agent which, when heated due to the irradiation with laser light or IR light to temperatures above 50° C., forms a gas which foams the matrix material by decomposition, chemical conversion or reaction.