I have a scene in which I have a floor and walls with some rocks placed here and there, I want to create the effect as if the wall and some rocks are daubed with graffiti. A text that would both be overlaying the some rocks and the wall at the same time (so not individually). Can someone share some ideas on how to create such thing?
Look for tutorials about applying a decal in C4D, but in a nutshell you will be duplicating your material and placing your text image in the alpha channel of the duplicated material (and generally turning off the other channels unless you want to modify the look of the text). Make a polygon selection of the area on your object that you want the text to appear, save it as a selection tag, and then drag that tag into the Selection window of your second material's Texture Tag. Turn off tiling, and adjust the position and scale of the text image in the Offset U, V and Length U, V settings.