1. In a visual display system of the computer generated image type, for a ground-based flight simulator, providing a rectangular raster scanned, perspective-transformed, pilot's visual display of a simulated textured surface, the improvement comprising the provision of a surface detail generator comprising a perspective transformation computer and a surface texture detail store, the perspective transformation computer being a pipelined calculator for computing in real time the perspective transformation from the display system display plane to the simulated surface plane continuously during simulated flight, and correspondingly scanning the surface texture detail store to provide texture for each element of the said rectangular raster scanned pilot's visual display.