When you attempt load a large image draped over a grid file in 3D the image does not show. You only see a grey and white shadow effect.

This occurs when that raster exceeds the available GPU graphics memory. Note that the memory consumed will be larger than the original raster image file. You can approximately calculate the required graphics card memory by -

This usually not of a problem for the DEM/Topographic grid as this is resize to a low resolution when the mesh wireframe is created in-memory to drape on.

1. Save the image as a uncompressed bitmap .bmp file. As the image will be loaded uncompressed into graphics memory.

2. Multiply the size 2-3x as Discover3D is not optimised and will often load multiple copies in memory.

As a workaround either upgrade your graphics card or resample to image to a lower resolution using Windows Photos or other free image tools.