Dielectric and plasmonic metasurfaces provide excellent control over the shaping of optical wavefronts via the manipulation of polarisation, phase and amplitude of the light. Taking advantage of their subwavelength thicknesses, metasurfaces have shown to be a very promising technology in a variety of applications including beam steering and focusing, polarisation and angular momentum control, enhancement of nonlinear effects, as well as holographic information encoding for 3D displays. Recently, the emergence of virtual reality and augmented reality technologies have led to the constant demand of effective techniques for the 2D visualisation of 3D objects. Normal mapping, for example, is widely used in computer graphics to create shading effects and recreate 3D-like features of surface textures, such as regular patterns, bumps or ripples. Here, we report on the development of the concept of surface normal mapping for the representation of 3D objects and shading effects with optical metasurfaces. In this work, the metasurface is designed to implement diffuse reflection and uses the concept of normal mapping to control its scattering properties. As a proof of principle, a flat diffuse metasurface imitating lighting and shading effects of a 3D cube was fabricated and characterised under incoherent illumination. The “3D image” is displayed directly on the illuminated metasurface and its shading varies in response to the change in illumination angle. The metasurface performs in a broad range of the visible spectrum, including the three main RGB wavelengths. The 3D images created via normal mapping based on optical metasurfaces provide an effective technology for 3D security features and anti-counterfeiting. This type of metasurfaces can also be useful in the design of efficient optical diffusers for display technology and etalons for metrology.