Using a 'window' images from the 'village' assets of Return to Castle Wolfenstein, the video above shows how textures can be used as a guide during the creation of more detailed or shaped meshes that can augment an already existing normal-mapped texture set (diffuse+normal+specular etc.)ScenarioIn certain situations there might be a need for in-game structures to be modelled to contain more detail than can otherwise be had using normal-mapped texture sets assigned to flat plains. If textures already exist it might be possible to use them as a template or guide around which a model can be made in Blender (or other application with the following support).
ProblemIn wanting to use pre-existing textures as a basis from which game models are to be made (and mapped using said-same images employed to make the mesh), editing can be tricky because UVW mapping tends not to be held in place during the generally 'destructive' modelling process - adding and moving edge-loops might shift or distort any UVW maps previously assigned for example. Whilst Blender has a number of properties available that might otherwise ease the UVW map distortion issue in a general sense, they do not always have a practical application. Ideally, rather than trying to prevent the problem the artist might find it better to 'ignore' it whilst being able to 'see' the texture at all time.
SolutionA 'see-through' mesh can be facilitated by making a duplication of an original Object (always work on a copy) and making any assigned assigned Material/s 'unique' (Single User data-blocks). Once done activate material "
Transparency" and reduce the value of the property so the mesh becomes see-through thus allowing the mesh to be editable in Edit mode; the mesh can be shaped whilst the original textured version is visible as a guide.