Image synthesis techniques are present in a wide range of applications as they leverage the amount of information required for creating realistic visualizations. For fast hardware rendering they usually employ a triangle-based representation describing the geometry of the scene. In this paper, we introduce a new and simple framework for performing on-the-fly refinement and simplification of meshes completely on the GPU. As we aim at making easy the integration of level-of-detail management into the creation workflow of artists, the presented method is easy to be implemented. We only need a coarse mesh, its displacement map and a geometry shader. At rendering time, we employ a geometry shader to parallelize the tessellation and displacement steps. The tessellation step performs uniform refinement or simplification operations by applying a fixed subdivision criterion. Our method also exploits coherence by taking advantage of the last computed mesh. We provide a method which offers a flexible integration with standard 3D tools, easy to be implemented, coherence exploitation and wholly processed by the GPU.